title: Phosphorylation of PTEN at STT motif is associated with DNA damage response.
abstract: Phosphatase and tensin homolog deleted on chromosome Ten (PTEN), a tumor suppressor protein participates in multiple cellular activities including DNA repair. In this work we found a relationship between phosphorylation of carboxy (C)-terminal STT motif of PTEN and DNA damage response. Ectopic expression of C-terminal phospho-mutants of PTEN, in PTEN deficient human glioblastoma cells, U87MG, resulted in reduced viability and DNA repair after etoposide induced DNA damage compared to cells expressing wild type PTEN. Also, after etoposide treatment phosphorylation of PTEN increased at C-terminal serine 380 and threonine 382/383 residues in PTEN positive HEK293T cells and wild type PTEN transfected U87MG cells. One-step further, DNA damage induced phosphorylation of PTEN was confirmed by immunoprecipitation of total PTEN from cellular extract followed by immunobloting with phospho-specific PTEN antibodies. Additionally, phospho-PTEN translocated to nucleus after etoposide treatment as revealed by indirect immunolabeling. Further, phosphorylation dependent nuclear foci formation of PTEN was observed after ionizing radiation or etoposide treatment which colocalized with γH2AX. Additionally, etoposide induced γH2AX, Mre11 and Ku70 foci persisted for a longer period of times in U87MG cells after ectopic expression of PTEN C-terminal phospho-mutant constructs compared to wild type PTEN expressing cells. Thus, our findings strongly suggest that DNA damage induced phosphorylation of C-terminal STT motif of PTEN is necessary for DNA repair.
authors.affiliation: Department of Life Science and Biotechnology, Jadavpur University, 188, Raja S.C. Mullick Road, Kolkata 700 032, West Bengal, India.
authors.forename: Sandip
authors.initials: S
authors.lastname: Misra
authors.affiliation: Department of Life Science and Biotechnology, Jadavpur University, 188, Raja S.C. Mullick Road, Kolkata 700 032, West Bengal, India.
authors.forename: Ananda
authors.initials: A
authors.lastname: Mukherjee
authors.affiliation: Department of Life Science and Biotechnology, Jadavpur University, 188, Raja S.C. Mullick Road, Kolkata 700 032, West Bengal, India. Electronic address: pkarmakar_28@yahoo.co.in.
authors.forename: Parimal
authors.initials: P
authors.lastname: Karmakar
mesh_terms: D000595:Amino Acid Sequence; D002478:Cells, Cultured; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics; D005047:Etoposide / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D051059:PTEN Phosphohydrolase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000378:metabolism
chemical_list: D013912:Threonine; D012694:Serine; D005047:Etoposide; D017346:Protein Serine-Threonine Kinases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human
keywords: DNA damage repair; Etoposide; Ku70; Mre11; Phosphatase and tensin homolog deleted from chromosome Ten (PTEN); Phosphorylation; γH2AX