Uncleaved TFIIA is a substrate for taspase 1 and active in transcription.
In higher eukaryotes, the large subunit of the general transcription factor TFIIA is encoded by the single TFIIAalphabeta gene and posttranslationally cleaved into alpha and beta subunits. The molecular mechanisms and biological significance of this proteolytic process have remained obscure. Here, we show that TFIIA is a substrate of taspase 1 as reported for the trithorax group mixed-lineage leukemia protein. We demonstrate that recombinant taspase 1 cleaves TFIIA in vitro. Transfected taspase 1 enhances cleavage of TFIIA, and RNA interference knockdown of endogenous taspase 1 diminishes cleavage of TFIIA in vivo. In taspase 1-/- MEF cells, only uncleaved TFIIA is detected. In Xenopus laevis embryos, knockdown of TFIIA results in phenotype and expression defects. Both defects can be rescued by expression of an uncleavable TFIIA mutant. Our study shows that uncleaved TFIIA is transcriptionally active and that cleavage of TFIIA does not serve to render TFIIA competent for transcription. We propose that cleavage fine tunes the transcription regulation of a subset of genes during differentiation and development.
Zhou
Huiqing
H
NCMLS, Department of Molecular Biology, 191, Radboud University of Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
Spicuglia
Salvatore
S
Hsieh
James J-D
JJ
Mitsiou
Dimitra J
DJ
Høiby
Torill
T
Veenstra
Gert Jan C
GJ
Korsmeyer
Stanley J
SJ
Stunnenberg
Hendrik G
HG
D000595:Amino Acid Sequence; D000818:Animals; D002457:Cell Extracts; D002467:Cell Nucleus / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010447:Peptide Hydrolases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D035561:Transcription Factor TFIIA / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics*; D014981:Xenopus
D002457:Cell Extracts; D011994:Recombinant Proteins; D035561:Transcription Factor TFIIA; D010450:Endopeptidases; D010447:Peptide Hydrolases; C480823:taspase1, human