Biology subjects

Hussein, S. M. I.

Publications and source records attributed to Hussein, S. M. I..

4 recordsLinked to original sources

bioRxiv2021

MRG proteins are shared by multiple protein complexes with distinct functions

MRG15/MORF4L1 is a highly conserved protein in eukaryotes that contains a chromodomain recognizing H3K36me3 in chromatin. Intriguingly, it has been reported in the literature to interact with several different factors involved in chromatin modifications, gene regulation, alternative mRNA splicing and DNA repair by homologous recombination. In order to get a complete and reliable picture of associations in physiological conditions, we used genome editing and tandem affinity purification to analyze the stable native interactome of human MRG15, its paralog MRGX/MORF4L2 that lacks the chromodomain, and MRGBP (MRG-binding protein) in isogenic K562 cells. We found stable interchangeable association of MRG15 and MRGX with the NuA4/TIP60 histone acetyltransferase/chromatin remodeler, Sin3B histone deacetylase/demethylase, ASH1L histone methyltransferase and PALB2/BRCA2 DNA repair protein complexes. These associations were further confirmed and analyzed by CRISPR-tagging of endogenous proteins and comparison of expressed isoforms. Importantly, based on structural information, point mutations could be introduced that can specifically disrupt MRG15 association with some complexes but not others. Most interestingly, we also identified a new abundant native complex formed by MRG15/X-MRGBP-BRD8-EP400NL that is functionally similar to the yeast TINTIN (Trimer Independent of NuA4 for Transcription Interactions with Nucleosomes) complex. Our results show that EP400NL, being homologous to the N-terminal region of NuA4/TIP60 subunit EP400, creates TINTIN by competing for BRD8 association. Functional genomics indicate that human TINTIN plays a role in transcription of specific genes. This is most likely linked to the H4ac-binding bromodomain of BRD8 along the H3K36me3-binding chromodomain of MRG15 on the coding region of transcribed genes. Taken together, our data provide a complete detailed picture of human MRG proteins-associated protein complexes which is essential to understand and correlate their diverse biological functions in chromatin-based nuclear processes. HighlightsO_LIMRG15 and MRGX are stably associated with several different protein complexes important for genome expression and stability. C_LIO_LISeveral MRG-containing complexes are chromatin modifiers. C_LIO_LISpecific point mutations in the MRG domain differentially affect associated complexes. C_LIO_LIA major human complex homologous to the yeast TINTIN complex is identified. C_LIO_LIThe protein EP400NL competes with EP400 to functionally separate TINTIN from the NuA4/TIP60 complex. C_LIO_LITINTIN contains a bromodomain and a chromodomain to regulate transcription. C_LI

molecular biology↗

bioRxiv2021

Signal requirement for cortical potential of transplantable human neuroepithelial stem cells

The cerebral cortex develops from dorsal forebrain neuroepithelial progenitor cells. Initial expansion of the progenitor cell pool is followed by the generation of neurons of all the cortical layers and later, astrocytes and oligodendrocytes. However, the regulatory pathways that control the expansion and maintenance of the neuroepithelial progenitor cell pool are currently unknown. Here we define six basic pathway components that regulate proliferation of cortically specified human neuroepithelial stem cells (cNESCs) in vitro without the loss of developmental potential. We show that activation of FGF and inhibition of BMP and ACTIVIN A signalling are required for long-term cNESC proliferation. We also demonstrate that cNESCs preserve dorsal telencephalon-specific potential when GSK3, AKT and nuclear CATENIN-{beta}1 activity are low. Remarkably, regulation of these six pathway components supports the clonal expansion of cNESCs. Moreover, cNESCs differentiate to lower and upper layer cortical neurons both in vitro and in vivo. Identifying the mechanisms that drive the self-renewal and fate of cNESCs decision of neuroepithelial stem cells is key to developing new stem cell-based therapeutic approaches to treat neurological conditions.

developmental biology↗

bioRxiv2021

Oncogenic ZMYND11-MBTD1 fusion protein anchors the NuA4/TIP60 histone acetyltransferase complex to the coding region of active genes

A chromosomal translocation found in cannibalistic acute myeloid leukemia (AML) leads to an in-frame fusion of the transcription elongation repressor ZMYND11 to MBTD1, a subunit of the NuA4/TIP60 histone acetyltransferase (HAT) complex. In contrast to the NuA4/TIP60 complex, ZMYND11 is linked to repression of actively transcribed genes through recognition of H3.3K36me3. To understand the abnormal molecular events that expression of this ZMYND11-MBTD1 fusion protein can create, we performed its biochemical and functional characterization in comparison to each individual fusion partner. ZMYND11-MBTD1 is stably incorporated into the endogenous NuA4/TIP60 complex but does not bring any additional interactors as the fusion lacks the MYND domain of ZMYND11. Nevertheless, this truncated ZMYND11 moiety in the fusion leads to mislocalization of the NuA4/TIP60 complex on the body of genes normally bound by ZMYND11 in the genome, in a PWWP-H3.3K36me3 interaction-dependent manner. This can be correlated to increased chromatin acetylation and altered gene transcription, most notably on the MYC oncogene, and alternative splicing. Importantly, expression of ZMYND11-MBTD1, but not the individual fusion partners, during embryonic stem cell differentiation, leads to decreased expression of specific differentiation markers, while favoring Myc-driven pluripotency. It also favors self-renewal of hematopoietic stem/progenitor cells. Altogether, these results indicate that the ZMYND11-MBTD1 fusion protein functions primarily by mistargeting the NuA4/TIP60 complex to the body of genes, altering normal transcription of specific genes, likely driving oncogenesis in part through the Myc regulatory network. Highlights-A recurrent chromosomal translocation detected in cannibalistic acute myeloid leukemia leads to the production of a ZMYND11-MBTD1 fusion protein. -The ZMYND11-MBTD1 fusion protein is stably incorporated into the endogenous NuA4/TIP60 complex. -ZMYND11-MBTD1 leads to mistargeting of NuA4/TIP60 activity to the coding region of ZMYND11-target genes, altering gene expression and splicing. -ZMYND11-MBTD1 binds the MYC gene leading to its upregulation, favoring growth and pluripotency while inhibiting differentiation markers.

molecular biology↗

bioRxiv2021

Misregulation of translation drives prostate cancer drug resistance

Emerging evidence associates translation factors and regulators to tumorigenesis. Recent advances in our ability to perform global translatome analyses indicate that our understanding of translational changes in cancer resistance is still limited. Here, we generated an enzalutamide-resistant prostate cancer (PCa) model, which recapitulated key features of clinical enzalutamide-resistant PCa. Using this model and polysome profiling, we investigated global translation changes that occur during the acquisition of PCa resistance. We found that enzalutamide-resistant cells exhibit a discordance in biological pathways affected in their translatome relative to their transcriptome, a deregulation of proteins involved in translation, and an overall decrease in translational efficiency. We also show that genomic alterations in proteins with high translational efficiency in enzalutamide-resistant cells are good predictors of poor patient prognosis. Additionally, long non-coding RNAs in enzalutamide-resistant cells show increased association with ribosomes, higher translation efficiency, and an even stronger correlation with poor patient prognosis. Taken together, this suggests that aberrant translation of coding and non-coding genes are strong indicators of PCa enzalutamide-resistance. Our findings thus point towards novel therapeutic avenues that may target enzalutamide resistant PCa.

cancer biology↗