Biology subjects

Deshpande, C.

Publications and source records attributed to Deshpande, C..

5 recordsLinked to original sources

bioRxiv2025

The structure and composition of native human nucleosomes

Since the first high-resolution structures of recombinantly assembled nucleosomes, efforts have shifted towards understanding chromatin structure in a native context. Most of these efforts have focused on native-like, yet still recombinantly assembled, nucleosomes that contain native DNA sequences. To date, no high-resolution structures of native human nucleosomes have been reported. Here we report the high-resolution cryo-EM structure of native human nucleosomes isolated from HEK293 cells. The HEK293-NCP structure reveals that native human nucleosomes store 145 bp of DNA. Despite the DNA sequence diversity of native nucleosomes, we observe conserved nucleotides that support the idea of a nucleosome positioning code. In addition to these striking features of nucleosomal DNA, we note alternate conformations of several DNA contacting histone residues that hint at dynamics in the HEK293-NCP. To complement the HEK293-NCP structure, we provide a mass spectrometry analysis of histone modifications and variants present in the sample, which demonstrates that a typical HEK293-NCP is composed of canonical histones with N-terminal tails that are methylated at K9, K27 and/or K36 of histone H3. Altogether these findings have implications for biological processes such as chromatin remodelling and transcription and improve our understanding of nucleosome and chromatin structure in a native context.

biochemistry↗

bioRxiv2023

ZNF512B binds RBBP4 via a variant NuRD interaction motif and aggregates chromatin in a NuRD complex-independent manner

The evolutionarily conserved histone variant H2A.Z plays a crucial role in various DNA-based processes but the underlying mechanisms by which it acts are not completely understood. Recently, we identified the zinc finger protein ZNF512B as an H2A.Z-, HMG20A- and PWWP2A-associated protein. Here, we report that ZNF512B binds the nucleosome remodeling and deacetylase (NuRD) complex. We discover a conserved amino acid sequence within ZNF512B that resembles the NuRD-interaction motif (NIM) previously identified in FOG-1 and other transcriptional regulators. By solving the crystal structure of this motif bound to the NuRD component RBBP4 and by applying several biochemical assays we demonstrate that this internal NIM is both necessary and sufficient for robust NuRD binding. Transcriptome analyses and reporter assays identify ZNF512B as a repressor of gene expression that can act in both NuRD-dependent and -independent ways. Surprisingly, high levels of ZNF512B expression lead to nuclear protein and chromatin aggregation foci that form independent of the interaction with the NuRD complex but depend on the zinc finger domains of ZNF512B. Our study has implications for diseases in which ZNF512B expression is deregulated, such as cancer and neurodegenerative diseases, and hint at the existence of more proteins as potential NuRD interactors.

molecular biology↗

bioRxiv2022

The role of auxiliary domains in modulating CHD4 activity suggests mechanistic commonality between enzyme families

CHD4 is an essential, widely conserved ATP-dependent translocase that is also a broad tumour dependency. In common with other SF2-family chromatin remodelling enzymes, it alters chromatin accessibility by repositioning histone octamers. Besides the helicase and adjacent tandem chromodomains and PHD domains, CHD4 features 1000 residues of N- and C-terminal sequence with unknown structure and function. We demonstrate that these regions regulate CHD4 activity through different mechanisms. An N-terminal intrinsically disordered region (IDR) promotes remodelling integrity in a manner that depends on the composition but not sequence of the IDR. The C-terminal region harbours an auto-inhibitory region that contacts the helicase domain. Auto-inhibition is relieved by a previously unrecognized C-terminal SANT-SLIDE domain split by [~]150 residues of disordered sequence, most likely by binding of this domain to substrate DNA. Our data shed light on CHD4 regulation and reveal strong mechanistic commonality between CHD family members, as well as with ISWI-family remodellers.

biochemistry↗

bioRxiv2021

Detection of pathogenic splicing events from RNA-sequencing data using dasper

Although next-generation sequencing technologies have accelerated the discovery of novel gene-to-disease associations, many patients with suspected Mendelian diseases still leave the clinic without a genetic diagnosis. An estimated one third of these patients will have disorders caused by mutations impacting splicing. RNA-sequencing has been shown to be a promising diagnostic tool, however few methods have been developed to integrate RNA-sequencing data into the diagnostic pipeline. Here, we introduce dasper, an R/Bioconductor package that improves upon existing tools for detecting aberrant splicing by using machine learning to incorporate disruptions in exon-exon junction counts as well as coverage. dasper is designed for diagnostics, providing a rank-based report of how aberrant each splicing event looks, as well as including visualization functionality to facilitate interpretation. We validate dasper using 16 patient-derived fibroblast cell lines harbouring pathogenic variants known to impact splicing. We find that dasper is able to detect pathogenic splicing events with greater accuracy than existing LeafCutterMD or z-score approaches. Furthermore, by only applying a broad OMIM gene filter (without any variant-level filters), dasper is able to detect pathogenic splicing events within the top 10 most aberrant identified for each patient. Since using publicly available control data minimises costs associated with incorporating RNA-sequencing into diagnostic pipelines, we also investigate the use of 504 GTEx fibroblast samples as controls. We find that dasper leverages publicly available data effectively, ranking pathogenic splicing events in the top 25. Thus, we believe dasper can increase diagnostic yield for a pathogenic splicing variants and enable the efficient implementation of RNA-sequencing for diagnostics in clinical laboratories.

bioinformatics↗

bioRxiv2018

Genetic variation within genes associated with mitochondrial function is significantly associated with later age at onset of Parkinson disease and contributes to disease risk

Mitochondrial dysfunction has been implicated in the aetiology of monogenic Parkinsons disease (PD). Yet the role that mitochondrial processes play in the most common form of the disease; sporadic PD, is yet to be fully established. Here we comprehensively assessed the role of mitochondrial function associated genes in sporadic PD by leveraging improvements in the scale and analysis of PD GWAS data with recent advances in our understanding of the genetics of mitochondrial disease. First, we identified that a proportion of the \"missing heritability\" of the PD can be explained by common variation within genes implicated in mitochondrial disease (primary gene list) and mitochondrial function (secondary gene list). Next we calculated a mitochondrial-specific polygenic risk score (PRS) and showed that cumulative small effect variants within both our primary and secondary gene lists are significantly associated with increased PD risk. Most significantly we further report that the PRS of the secondary mitochondrial gene list was significantly associated with later age at onset. Finally, to identify possible functional genomic associations we implemented Mendelian randomisation, which showed that 14 of these mitochondrial function associated genes showed functional consequence associated with PD risk. Further analysis suggested that the 14 identified genes are not only involved in mitophagy but implicate new mitochondrial processes. Our data suggests that therapeutics targeting mitochondrial bioenergetics and proteostasis pathways distinct from mitophagy could be beneficial to treating the early stage of PD.

genetics↗