The histone H4 lysine 20 demethylase DPY-21 regulates the dynamics of condensin DC binding.

Laura Breimann,Andrew Woehler,Maxwell Kramer,Ana Karina Morao,Sarah E Albritton,Jun Kim,Sevinç Ercan,Ella Bahry,Michael J Carrozza,Kustrim Cerimi,Vic-Fabienne Schumann,Stephan Preibisch,Krishna Bikkasani,Lena Annika Street,David Sebastian Jimenez,Nina Maryn

doi:10.1242/jcs.258818

Abstract

ABSTRACTCondensin is a multi-subunit structural maintenance of chromosomes (SMC) complex that binds to and compacts chromosomes. Here, we addressed the regulation of condensin binding dynamics using Caenorhabditis elegans condensin DC, which represses X chromosomes in hermaphrodites for dosage compensation. We established fluorescence recovery after photobleaching (FRAP) using the SMC4 homolog DPY-27 and showed that a well-characterized ATPase mutation abolishes DPY-27 binding to X chromosomes. Next, we performed FRAP in the background of several chromatin modifier mutants that cause varying degrees of X chromosome derepression. The greatest effect was in a null mutant of the H4K20me2 demethylase DPY-21, where the mobile fraction of condensin DC reduced from ∼30% to 10%. In contrast, a catalytic mutant of dpy-21 did not regulate condensin DC mobility. Hi-C sequencing data from the dpy-21 null mutant showed little change compared to wild-type data, uncoupling Hi-C-measured long-range DNA contacts from transcriptional repression of the X chromosomes. Taken together, our results indicate that DPY-21 has a non-catalytic role in regulating the dynamics of condensin DC binding, which is important for transcription repression.

Highlights

The evolutionarily conserved structural maintenance of chromosomes (SMC) complexes use the energy from ATP hydrolysis to regulate chromosome structure in various nuclear processes (Hirano, 2016)
Our results suggest that DPY-21 has a noncatalytic role in regulating the dynamics of condensin DC binding to the X chromosomes, which is important for its function in transcription repression
We set up the fluorescence recovery after photobleaching (FRAP) system using DPY-27, the SMC4 homolog that distinguishes condensin DC from I (Fig. 1A)

Summary

Introduction

The evolutionarily conserved structural maintenance of chromosomes (SMC) complexes use the energy from ATP hydrolysis to regulate chromosome structure in various nuclear processes (Hirano, 2016). Unlike a related SMC complex called cohesin, the proteins and chromatin factors that regulate the dynamics of condensin binding are less clear (Paul et al, 2018b). We addressed this question using the Caenorhabditis elegans dosage compensation system, where an X-specific condensin binding and function is better understood and serves as a model for the metazoan condensins (Albritton and Ercan, 2018). In C. elegans, X chromosome dosage compensation is mediated by a specialized condensin that forms the core of the dosage compensation complex (DCC) (Meyer, 2005) This X-specific condensin (hereafter condensin DC) is distinguished from the canonical condensin I by a single SMC-4 variant called DPY-27 (Csankovszki et al, 2009). A subset of the strong rex sites serve as blocks to condensin DC movement, insulating DNA contacts and forming loop-anchored topologically associating domains (TADs) (Crane et al, 2015; Jimenez et al, 2021)

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Results

Conclusion