Differential localization and high expression of SURVIVIN splice variants in human embryonic stem cells but not in differentiated cells implicate a role for SURVIVIN in pluripotency.
The BIRC5 gene encodes the oncofetal protein SURVIVIN, as well as four additional splice variants (ΔEx3, 2B, 3B and 2α). SURVIVIN, an inhibitor of apoptosis, is also a chromosomal passenger protein (CPP). Previous results have demonstrated that SURVIVIN is expressed at high levels in embryonic stem cells and inhibition of SURVIVIN function results in apoptosis, however these studies have not investigated the other four splice variants. In this study, we demonstrate that all variants are expressed at significantly higher levels in human embryonic stem (hES) cells than in differentiated cells. We examined the subcellular localization of the three most highly expressed variants. SURVIVIN displayed canonical CPP localization in mitotic cells and cytoplasmic localization in interphase cells. In contrast, SURVIVIN-ΔEx3 and SURVIVIN-2B did not localize as a CPP; SURVIVIN-ΔEx3 was found constitutively in the nucleus while SURVIVIN-2B was distributed along the chromosomes during mitosis and also to the mitotic spindle poles. We used inducible shRNA against SURVIVIN to inhibit expression in a titratable fashion. Using this system, we reduced the mRNA levels of these three variants to approx. 40%, resulting in a concomitant reduction of OCT4 and NANOG mRNA, suggesting a role for the SURVIVIN variants in pluripotency.
Department of Biology, University of Texas at San Antonio, San Antonio, TX 78249, United States.
Amber N
AN
Mull
Department of Biology, University of Texas at San Antonio, San Antonio, TX 78249, United States.
Amanda
A
Klar
Department of Biology, University of Texas at San Antonio, San Antonio, TX 78249, United States. Electronic address: Christopher.Navara@utsa.edu.
Christopher S
CS
Navara
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000166:cytology* / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D050814:Octamer Transcription Factor-3 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D039904:Pluripotent Stem Cells / Q000166:cytology* / Q000378:metabolism*; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000235:genetics; D000077022:Survivin
C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; C494174:Pou5f1 protein, mouse; D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000077022:Survivin