Project description:FACT was discovered to be a repressor of transcription in mES cells. In addition, the murine endogenous retrovirus were repressed by various mechanisms. Hence, we examined the possibility for Ssrp1 as a repressor of MT2/MERVL.
Project description:Estrogen Receptor alpha (ERα) is a key driver of most breast cancers, and it is the target of endocrine therapies used in the clinic to treat women with ERα positive (ER+) breast cancer. The two methods ChIP-seq (chromatin immunoprecipitation coupled with deep sequencing) and RIME (Rapid Immunoprecipitation of Endogenous Proteins) have greatly improved our understanding of ERα function during breast cancer progression and in response to anti-estrogens. A critical component of both ChIP-seq and RIME protocols is the antibody that is used to pull down the bait protein. To date, most of the ChIP-seq and RIME experiments for the study of ERα have been performed using the sc-543 antibody from Santa Cruz Biotechnology. However, this antibody has been discontinued, thereby severely impacting the study of ERα in normal physiology as well as diseases such as breast cancer and ovarian cancer. Here, we compare the sc-543 antibody with other commercially available antibodies, and we show that 06-935 (EMD Millipore) and ab3575 (Abcam) antibodies can successfully replace the sc-543 antibody for ChIP-seq and RIME experiments.
Project description:Endogenous retroviruses (ERVs) were usually silenced by various histone modifications on histone H3 variants and respective histone chaperones in embryonic stem cells (ESCs). However, it is still unknown whether chaperones of other histones could repress ERVs. Here, we show that H2A/H2B histone chaperone FACT plays a critical role in silencing ERVs and ERV-derived cryptic promoters in ESCs. Loss of FACT component Ssrp1 activated MERVL whereas the re-introduction of Ssrp1 rescued the phenotype. Additionally, Ssrp1 interacted with MERVL and suppressed cryptic transcription of MERVL-fused genes. Remarkably, Ssrp1 interacted with and recruited H2B deubiquitinase Usp7 to Ssrp1 target genes. Suppression of Usp7 caused similar phenotypes as loss of Ssrp1. Furthermore, Usp7 acted by deubiquitinating H2Bub and thereby repressed the expression of MERVL-fused genes. Taken together, our study uncovers a unique mechanism by which FACT complex silences ERVs and ERV-derived cryptic promoters in ESCs.
Project description:Endogenous retrovirus MERVL is specifically expressed in a minority of embryonic stem cells. To determine the restrain mechanism of MERVL, we knocked out Ssrp1 and analyzed the effect on the expression of transposable elements and coding genes. Ssrp1 further interacts with ubiquitin specific protease Usp7. We knocked down usp7 and analyzed the effect on the expression of MERVL. It turns out the deletion of ssrp1 or usp7 would lead to upregulation of MERVL. This study extends our understandings of the machanism by novel factors regulates MERVL.
Project description:Endogenous retrovirus MERVL is specifically expressed in a minority of embryonic stem cells. To determine the restrain mechanism of MERVL, we knocked out Ssrp1 and analyzed the effect on the expression of transposable elements and coding genes.
