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Dephosphorylation Enables the Recruitment of 53BP1 to Double-Strand DNA Breaks
Lee, D.H.,Acharya, Sanket S.,Kwon, M.,Drane, P.,Guan, Y.,Adelmant, G.,Kalev, P.,Shah, J.,Pellman, D.,Marto, Jarrod A.,Chowdhury, D. Cell Press 2014 Molecular cell Vol.54 No.3
Excluding 53BP1 from chromatin is required to attenuate the DNA damage response during mitosis, yet the functional relevance and regulation of this exclusion are unclear. Here we show that 53BP1 is phosphorylated during mitosis on two residues, T1609 and S1618, located in its well-conserved ubiquitination-dependent recruitment (UDR) motif. Phosphorylating these sites blocks the interaction of the UDR motif with mononuclesomes containing ubiquitinated histone H2A and impedes binding of 53BP1 to mitotic chromatin. Ectopic recruitment of 53BP1-T1609A/S1618A to mitotic DNA lesions was associated with significant mitotic defects that could be reversed by inhibiting nonhomologous end-joining. We also reveal that protein phosphatase complex PP4C/R3β dephosphorylates T1609 and S1618 to allow the recruitment of 53BP1 to chromatin in G1 phase. Our results identify key sites of 53BP1 phosphorylation during mitosis, identify the counteracting phosphatase complex that restores the potential for DDR during interphase, and establish the physiological importance of this regulation.
Anand K. Sajnani,Sanket G. Shah,Mudasir Rashid,Abhiram Natu,Poonam B. Gera,Sanjay Gupta 전남대학교 의과학연구소 2021 전남의대학술지 Vol.57 No.3
Histone modifications have been demonstrated to play a significant role in oral squamous cell carcinoma (OSCC) epigenetic regulation. An in-silico analysis of The Cancer Genome Atlas (TCGA) of various histone acetyl transferases (HATs) and histone deacetylases (HDACs) suggested that HATs do not differ between normal and tumor samples whereas HDAC2 and HDAC1 change maximally and marginally respectively between normal and tumor patients with no change being noted in HDAC6 expression. Hence, this investigation was carried out to validate the expression states of HDAC 1, 2 and 6 mRNAs in buccal mucosa and tongue SCC samples in an Indian cohort. Buccal mucosa and tongue squamous cell carcinoma tissues with intact histopathology were processed for RNA isolation followed by cDNA synthesis which was then subjected to q-PCR for HDACs. The average RNA yield of the tongue tissue sample was ∼2 mg/mg of tissue and the A260/280 ratios were between 2.03 and 2.06. The average RNA yield of buccal mucosa tissue sample was ∼1 mg/mg of tissue and the A260/280 ratio were between 2.00 and 2.08. We have demonstrated that HDAC2 was overexpressed in tongue and buccal mucosa samples. Over-expression of HDAC2 imply potential use of HDACi along with standard chemotherapeutic drug in oral cancer treatment.