TBP2 is a substitute for TBP in Xenopus oocyte transcription.
BACKGROUND
TATA-box-binding protein 2 (TBP2/TRF3) is a vertebrate-specific paralog of TBP that shares with TBP a highly conserved carboxy-terminal domain and the ability to bind the TATA box. TBP2 is highly expressed in oocytes whereas TBP is more abundant in embryos.


RESULTS
We find that TBP2 is proteolytically degraded upon meiotic maturation; after germinal vesicle breakdown relatively low levels of TBP2 expression persist. Furthermore, TBP2 localizes to the transcriptionally active loops of lampbrush chromosomes and is recruited to a number of injected promoters in oocyte nuclei. Using an altered binding specificity mutant reporter system we show that TBP2 promotes RNA polymerase II transcription in vivo. Intriguingly, TBP, which in oocytes is undetectable at the protein level, can functionally replace TBP2 when ectopically expressed in oocytes, showing that switching of initiation factors can be driven by changes in their expression. Proteolytic degradation of TBP2 is not required for repression of transcription during meiotic maturation, suggesting a redundant role in this repression or a role in initiation factor switching between oocytes and embryos.


CONCLUSIONS
The expression and transcriptional activity of TBP2 in oocytes show that TBP2 is the predominant initiation factor in oocytes, which is substituted by TBP on a subset of promoters in embryos as a result of proteolytic degradation of TBP2 during meiotic maturation.
Akhtar
Waseem
W
Department of Molecular Biology, Faculty of Science, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen, The Netherlands. w.akhtar@ncmls.ru.nl
Veenstra
Gert Jan C
GJ
D000818:Animals; D002453:Cell Cycle / Q000235:genetics*; D047369:Chromatin Immunoprecipitation; D002875:Chromosomes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation; D008845:Microinjections; D008954:Models, Biological; D009865:Oocytes / Q000254:growth & development / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000502:physiology; D014176:Protein Biosynthesis; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D016385:TATA Box / Q000502:physiology*; D035181:TATA-Box Binding Protein / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D014981:Xenopus / Q000235:genetics / Q000254:growth & development; D029867:Xenopus Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology
D004268:DNA-Binding Proteins; D035181:TATA-Box Binding Protein; C492584:TBPL2 protein, Xenopus; D029867:Xenopus Proteins; D012319:RNA Polymerase II