Publications by authors named "Artem Bonchuk"

13 Publications

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Mechanism and functional role of the interaction between CP190 and the architectural protein Pita in Drosophila melanogaster.

Epigenetics Chromatin 2021 Mar 22;14(1):16. Epub 2021 Mar 22.

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 3 4/5 Vavilov St., Moscow, 119334, Russia.

Background: Pita is required for Drosophila development and binds specifically to a long motif in active promoters and insulators. Pita belongs to the Drosophila family of zinc-finger architectural proteins, which also includes Su(Hw) and the conserved among higher eukaryotes CTCF. The architectural proteins maintain the active state of regulatory elements and the long-distance interactions between them. In particular, Pita is involved in the formation of several boundaries between regulatory domains that controlled the expression of three hox genes in the Bithorax complex (BX-C). The CP190 protein is recruited to chromatin through interaction with the architectural proteins.

Results: Using in vitro pull-down analysis, we precisely mapped two unstructured regions of Pita that interact with the BTB domain of CP190. Then we constructed transgenic lines expressing the Pita protein of the wild-type and mutant variants lacking CP190-interacting regions. We have demonstrated that CP190-interacting region of the Pita can maintain nucleosome-free open chromatin and is critical for Pita-mediated enhancer blocking activity in BX-C. At the same time, interaction with CP190 is not required for the in vivo function of the mutant Pita protein, which binds to the same regions of the genome as the wild-type protein. Unexpectedly, we found that CP190 was still associated with the most of genome regions bound by the mutant Pita protein, which suggested that other architectural proteins were continuing to recruit CP190 to these regions.

Conclusions: The results directly demonstrate role of CP190 in insulation and support a model in which the regulatory elements are composed of combinations of binding sites that interact with several architectural proteins with similar functions.
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http://dx.doi.org/10.1186/s13072-021-00391-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7983404PMC
March 2021

Structural basis of diversity and homodimerization specificity of zinc-finger-associated domains in Drosophila.

Nucleic Acids Res 2021 02;49(4):2375-2389

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia.

In arthropods, zinc finger-associated domains (ZADs) are found at the N-termini of many DNA-binding proteins with tandem arrays of Cys2-His2 zinc fingers (ZAD-C2H2 proteins). ZAD-C2H2 proteins undergo fast evolutionary lineage-specific expansion and functional diversification. Here, we show that all ZADs from Drosophila melanogaster form homodimers, but only certain ZADs with high homology can also heterodimerize. CG2712, for example, is unable to heterodimerize with its paralog, the previously characterized insulator protein Zw5, with which it shares 46% homology. We obtained a crystal structure of CG2712 protein's ZAD domain that, in spite of a low sequence homology, has similar spatial organization with the only known ZAD structure (from Grauzone protein). Steric clashes prevented the formation of heterodimers between Grauzone and CG2712 ZADs. Using detailed structural analysis, site-directed mutagenesis, and molecular dynamics simulations, we demonstrated that rapid evolutionary acquisition of interaction specificity was mediated by the more energy-favorable formation of homodimers in comparison to heterodimers, and that this specificity was achieved by multiple amino acid substitutions resulting in the formation or breaking of stabilizing interactions. We speculate that specific homodimerization of ZAD-C2H2 proteins is important for their architectural role in genome organization.
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http://dx.doi.org/10.1093/nar/gkab061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7913770PMC
February 2021

N-terminal domain of the architectural protein CTCF has similar structural organization and ability to self-association in bilaterian organisms.

Sci Rep 2020 02 14;10(1):2677. Epub 2020 Feb 14.

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia.

CTCF is the main architectural protein found in most of the examined bilaterian organisms. The cluster of the C2H2 zinc-finger domains involved in recognition of long DNA-binding motif is only part of the protein that is evolutionarily conserved, while the N-terminal domain (NTD) has different sequences. Here, we performed biophysical characterization of CTCF NTDs from various species representing all major phylogenetic clades of higher metazoans. With the exception of Drosophilides, the N-terminal domains of CTCFs show an unstructured organization and absence of folded regions in vitro. In contrast, NTDs of Drosophila melanogaster and virilis CTCFs contain unstructured folded regions that form tetramers and dimers correspondingly in vitro. Unexpectedly, most NTDs are able to self-associate in the yeast two-hybrid and co-immunoprecipitation assays. These results suggest that NTDs of CTCFs might contribute to the organization of CTCF-mediated long-distance interactions and chromosomal architecture.
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http://dx.doi.org/10.1038/s41598-020-59459-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021899PMC
February 2020

Small Drosophila zinc finger C2H2 protein with an N-terminal zinc finger-associated domain demonstrates the architecture functions.

Biochim Biophys Acta Gene Regul Mech 2020 01 6;1863(1):194446. Epub 2019 Nov 6.

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow 119334, Russia. Electronic address:

Recently, the concept has arisen that a special class of architectural proteins exists, which are responsible not only for global chromosome architecture but also for the local regulation of enhancer-promoter interactions. Here, we describe a new architectural protein, with a total size of only 375 aa, which contains an N-terminal zinc finger-associated domain (ZAD) and a cluster of five zinc finger C2H2 domains at the C-terminus. This new protein, named ZAD and Architectural Function 1 protein (ZAF1 protein), is weakly and ubiquitously expressed, with the highest expression levels observed in oocytes and embryos. The cluster of C2H2 domains recognizes a specific 15-bp consensus site, located predominantly in promoters, near transcription start sites. The expression of ZAF1 by a tissue-specific promoter led to the complete blocking of the eye enhancer when clusters of ZAF1 binding sites flanked the eye enhancer in transgenic lines, suggesting that the loop formed by the ZAF1 protein leads to insulation. The ZAF1 protein also supported long-range interactions between the yeast GAL4 activator and the white promoter in transgenic Drosophila lines. A mutant protein lacking the ZAD failed to block the eye enhancer or to support distance interactions in transgenic lines. Taken together, these results suggest that ZAF1 is a minimal architectural protein that can be used to create a convenient model for studying the mechanisms of distance interactions.
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http://dx.doi.org/10.1016/j.bbagrm.2019.194446DOI Listing
January 2020

The simultaneous interaction of MSL2 with CLAMP and DNA provides redundancy in the initiation of dosage compensation in males.

Development 2019 08 23;146(19). Epub 2019 Aug 23.

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, Moscow 119334, Russia

The binding of the male-specific lethal dosage compensation complex (DCC) exclusively to the male X chromosome provides an excellent model system to understand mechanisms of selective recruitment of protein complexes to chromatin. Previous studies showed that the male-specific organizer of the complex, MSL2, and the ubiquitous DNA-binding protein CLAMP are key players in the specificity of X chromosome binding. The CXC domain of MSL2 binds to genomic sites of DCC recruitment Another conserved domain of MSL2, named Clamp-binding domain (CBD) directly interacts with the N-terminal zinc-finger domain of CLAMP. Here, we found that inactivation of CBD or CXC individually only modestly affected recruitment of the DCC to the X chromosome in males. However, combination of these two genetic lesions within the same MSL2 mutant resulted in an increased loss of DCC recruitment to the X chromosome. Thus, proper MSL2 positioning requires an interaction with either CLAMP or DNA to initiate dosage compensation in males.
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http://dx.doi.org/10.1242/dev.179663DOI Listing
August 2019

Functional dissection of the developmentally restricted BEN domain chromatin boundary factor Insensitive.

Epigenetics Chromatin 2019 01 3;12(1). Epub 2019 Jan 3.

Department of Molecular Biology, Princeton University, Princeton, NJ, USA.

Background: Boundaries in the Drosophila bithorax complex delimit autonomous regulatory domains that activate the parasegment (PS)-specific expression of homeotic genes. The Fab-7 boundary separates the iab-6 and iab-7 regulatory domains that control Abd-B expression in PS11 and PS12. This boundary is composed of multiple functionally redundant elements and has two key activities: it blocks crosstalk between iab-6 and iab-7 and facilitates boundary bypass.

Results: Here, we have used a structure-function approach to elucidate the biochemical properties and the in vivo activities of a conserved BEN domain protein, Insensitive, that is associated with Fab-7. Our biochemical studies indicate that in addition to the C-terminal BEN DNA-binding domain, Insv has two domains that mediate multimerization: one is a coiled-coil domain in the N-terminus, and the other is next to the BEN domain. These multimerization domains enable Insv to bind simultaneously to two canonical 8-bp recognition motifs, as well as to a ~ 100-bp non-canonical recognition sequence. They also mediate the assembly of higher-order multimers in the presence of DNA. Transgenic proteins lacking the N-terminal coiled-coil domain are compromised for boundary function in vivo. We also show that Insv interacts directly with CP190, a protein previously implicated in the boundary functions of several DNA-binding proteins, including Su(Hw) and dCTCF. While CP190 interaction is required for Insv binding to a subset of sites on polytene chromosomes, it has only a minor role in the boundary activity of Insv in the context of Fab-7.

Conclusions: The subdivision of eukaryotic chromosomes into discrete topological domains depends upon the pairing of boundary elements. In flies, pairing interactions are specific and typically orientation dependent. They occur in cis between neighboring heterologous boundaries, and in trans between homologous boundaries. One potential mechanism for ensuring pairing-interaction specificity is the use of sequence-specific DNA-binding proteins that can bind simultaneously with two or more recognition sequences. Our studies indicate that Insv can assemble into a multivalent DNA-binding complex and that the N-terminal Insv multimerization domain is critical for boundary function.
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http://dx.doi.org/10.1186/s13072-018-0249-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6317261PMC
January 2019

The BEN Domain Protein Insensitive Binds to the Chromatin Boundary To Establish Proper Segmental Identity in .

Genetics 2018 10 6;210(2):573-585. Epub 2018 Aug 6.

Department of Molecular Biology, Princeton University, New Jersey 08544

Boundaries (insulators) in the bithorax complex (BX-C) delimit autonomous regulatory domains that orchestrate the parasegment (PS)-specific expression of the BX-C homeotic genes. The boundary separates the and regulatory domains, which control Abd-B expression in PS11 and PS12, respectively. This boundary is composed of multiple functionally redundant elements and has two key functions: it blocks cross talk between and and facilitates boundary bypass. Here, we show that two BEN domain protein complexes, Insensitive and Elba, bind to multiple sequences located in the nuclease hypersensitive regions. Two of these sequences are recognized by both Insv and Elba and correspond to a CCAATTGG palindrome. Elba also binds to a related CCAATAAG sequence, while Insv does not. However, the third Insv recognition sequences is ∼100 bp in length and contains the CCAATAAG sequence at one end. Both Insv and Elba are assembled into large complexes (∼420 and ∼265-290 kDa, respectively) in nuclear extracts. Using a sensitized genetic background, we show that the Insv protein is required for boundary function and that PS11 identity is not properly established in mutants. This is the first demonstration that a BEN domain protein is important for the functioning of an endogenous fly boundary.
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http://dx.doi.org/10.1534/genetics.118.301259DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6216583PMC
October 2018

Opbp is a new architectural/insulator protein required for ribosomal gene expression.

Nucleic Acids Res 2017 Dec;45(21):12285-12300

Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilova St., Moscow 119334, Russia.

A special class of poorly characterized architectural proteins is required for chromatin topology and enhancer-promoter interactions. Here, we identify Opbp as a new Drosophila architectural protein, interacting with CP190 both in vivo and in vitro. Opbp binds to a very restrictive set of genomic regions, through a rare sequence specific motif. These sites are co-bound by CP190 in vivo, and generally located at bidirectional promoters of ribosomal protein genes. We show that Opbp is essential for viability, and loss of opbp function, or destruction of its motif, leads to reduced ribosomal protein gene expression, indicating a functional role in promoter activation. As characteristic of architectural/insulator proteins, the Opbp motif is sufficient for distance-dependent reporter gene activation and enhancer-blocking activity, suggesting an Opbp-mediated enhancer-promoter interaction. Rather than having a constitutive role, Opbp represents a new type of architectural protein with a very restricted, yet essential, function in regulation of housekeeping gene expression.
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http://dx.doi.org/10.1093/nar/gkx840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5716193PMC
December 2017

Architectural proteins Pita, Zw5,and ZIPIC contain homodimerization domain and support specific long-range interactions in Drosophila.

Nucleic Acids Res 2016 09 2;44(15):7228-41. Epub 2016 May 2.

Institute of Gene Biology, Russian Academy of Sciences, Vavilova str. 34/5, Moscow 119334, Russia

According to recent models, as yet poorly studied architectural proteins appear to be required for local regulation of enhancer-promoter interactions, as well as for global chromosome organization. Transcription factors ZIPIC, Pita and Zw5 belong to the class of chromatin insulator proteins and preferentially bind to promoters near the TSS and extensively colocalize with cohesin and condensin complexes. ZIPIC, Pita and Zw5 are structurally similar in containing the N-terminal zinc finger-associated domain (ZAD) and different numbers of C2H2-type zinc fingers at the C-terminus. Here we have shown that the ZAD domains of ZIPIC, Pita and Zw5 form homodimers. In Drosophila transgenic lines, these proteins are able to support long-distance interaction between GAL4 activator and the reporter gene promoter. However, no functional interaction between binding sites for different proteins has been revealed, suggesting that such interactions are highly specific. ZIPIC facilitates long-distance stimulation of the reporter gene by GAL4 activator in yeast model system. Many of the genomic binding sites of ZIPIC, Pita and Zw5 are located at the boundaries of topologically associated domains (TADs). Thus, ZAD-containing zinc-finger proteins can be attributed to the class of architectural proteins.
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http://dx.doi.org/10.1093/nar/gkw371DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5009728PMC
September 2016

Functional role of dimerization and CP190 interacting domains of CTCF protein in Drosophila melanogaster.

BMC Biol 2015 Aug 7;13:63. Epub 2015 Aug 7.

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia.

Background: Insulators play a central role in gene regulation, chromosomal architecture and genome function in higher eukaryotes. To learn more about how insulators carry out their diverse functions, we have begun an analysis of the Drosophila CTCF (dCTCF). CTCF is one of the few insulator proteins known to be conserved from flies to man.

Results: In the studies reported here we have focused on the identification and characterization of two dCTCF protein interaction modules. The first mediates dCTCF multimerization, while the second mediates dCTCF-CP190 interactions. The multimerization domain maps in the N-terminus of the dCTCF protein and likely mediates the formation of tetrameric complexes. The CP190 interaction module encompasses a sequence ~200 amino acids long that spans the C-terminal and mediates interactions with the N-terminal BTB domain of the CP190 protein. Transgene rescue experiments showed that a dCTCF protein lacking sequences critical for CP190 interactions was almost as effective as wild type in rescuing the phenotypic effects of a dCTCF null allele. The mutation did, however, affect CP190 recruitment to specific Drosophila insulator elements and had a modest effect on dCTCF chromatin association. A protein lacking the N-terminal dCTCF multimerization domain incompletely rescued the zygotic and maternal effect lethality of the null and did not rescue the defects in Abd-B regulation evident in surviving adult dCTCF mutant flies. Finally, we show that elimination of maternally contributed dCTCF at the onset of embryogenesis has quite different effects on development and Abd-B regulation than is observed when the homozygous mutant animals develop in the presence of maternally derived dCTCF activity.

Conclusions: Our results indicate that dCTCF-CP190 interactions are less critical for the in vivo functions of the dCTCF protein than the N-terminal dCTCF-dCTCF interaction domain. We also show that the phenotypic consequences of dCTCF mutations differ depending upon when and how dCTCF activity is lost.
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http://dx.doi.org/10.1186/s12915-015-0168-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4528719PMC
August 2015

Two new insulator proteins, Pita and ZIPIC, target CP190 to chromatin.

Genome Res 2015 Jan 23;25(1):89-99. Epub 2014 Oct 23.

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, Moscow 119334, Russia

Insulators are multiprotein-DNA complexes that regulate the nuclear architecture. The Drosophila CP190 protein is a cofactor for the DNA-binding insulator proteins Su(Hw), CTCF, and BEAF-32. The fact that CP190 has been found at genomic sites devoid of either of the known insulator factors has until now been unexplained. We have identified two DNA-binding zinc-finger proteins, Pita, and a new factor named ZIPIC, that interact with CP190 in vivo and in vitro at specific interaction domains. Genomic binding sites for these proteins are clustered with CP190 as well as with CTCF and BEAF-32. Model binding sites for Pita or ZIPIC demonstrate a partial enhancer-blocking activity and protect gene expression from PRE-mediated silencing. The function of the CTCF-bound MCP insulator sequence requires binding of Pita. These results identify two new insulator proteins and emphasize the unifying function of CP190, which can be recruited by many DNA-binding insulator proteins.
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http://dx.doi.org/10.1101/gr.174169.114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4317163PMC
January 2015

Highly conserved ENY2/Sus1 protein binds to Drosophila CTCF and is required for barrier activity.

Epigenetics 2014 Sep 1;9(9):1261-70. Epub 2014 Aug 1.

Department of the Control of Genetic Processes; Institute of Gene Biology; Russian Academy of Sciences; Moscow, Russia.

Chromatin insulators affect interactions between promoters and enhancers/silencers and function as barriers for the spreading of repressive chromatin. Drosophila insulator protein dCTCF marks active promoters and boundaries of many histone H3K27 trimethylation domains associated with repressed chromatin. In particular, dCTCF binds to such boundaries between the parasegment-specific regulatory domains of the Bithorax complex. Here we demonstrate that the evolutionarily conserved protein ENY2 is recruited to the zinc-finger domain of dCTCF and is required for the barrier activity of dCTCF-dependent insulators in transgenic lines. Inactivation of ENY2 by RNAi in BG3 cells leads to the spreading of H3K27 trimethylation and Pc protein at several dCTCF boundaries. The results suggest that evolutionarily conserved ENY2 is responsible for barrier activity mediated by the dCTCF protein.
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http://dx.doi.org/10.4161/epi.32086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4169018PMC
September 2014

Drosophila BTB/POZ domains of "ttk group" can form multimers and selectively interact with each other.

J Mol Biol 2011 Sep 29;412(3):423-36. Epub 2011 Jul 29.

Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, Moscow 119334, Russia.

The BTB (bric-a-brac, tramtrack and broad complex)/POZ (poxvirus and zinc finger) domain is a conserved protein-protein interaction motif contained in a variety of transcription factors involved in development, chromatin remodeling, insulator activity, and carcinogenesis. All well-studied mammalian BTB domains form obligate homodimers and, rarely, tetramers. Only the BTB domain of the Drosophila GAGA factor (GAF) has been shown to exist as higher-order multimers. The BTB domain of GAF belongs to the "ttk group" that contains several highly conserved sequences not found in other BTB domains. Here, we have shown by size-exclusion chromatography, chemical cross-linking, and nondenaturing PAGE that four additional BTB domains of the ttk group-Batman, Mod(mdg4), Pipsqueak, and Tramtrack-can form multimers, like GAF. Interestingly, the BTB domains of GAF and Batman have formed a wide range of complexes and interacted in the yeast two-hybrid assay with other BTB domains tested. In contrast, the BTB domains of Mod(mdg4), Pipsqueak, and Tramtrack have formed stable high-order multimer complexes and failed to interact with each other. The BTB domain of Drosophila CP190 protein does not belong to the ttk group. This BTB domain has formed stable dimers and has not interacted with domains of the ttk group. Previously, it was suggested that GAF oligomerization into higher-order complexes facilitates long-range activation by providing a protein bridge between an enhancer and a promoter. Unexpectedly, experiments in the Drosophila model system have not supported the role of GAF in organization of long-distance interaction between the yeast GAL4 activator and the white promoter.
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http://dx.doi.org/10.1016/j.jmb.2011.07.052DOI Listing
September 2011