HTAF(II)68, A NOVEL RNA SSDNA-BINDING PROTEIN WITH HOMOLOGY TO THE PRO-ONCOPROTEINS TLS/FUS AND EWS IS ASSOCIATED WITH BOTH TFIID AND RNA-POLYMERASE-II/

TFIID is the main sequence-specific DNA-binding component of the RNA p olymerase II (Pol II) transcriptional machinery, It is a multiprotein complex composed of the TATA-binding protein (TBP) and TBP-associated factors (TAF(II)s). Here we report the cloning and characterization of a novel human TBP-associated factor, hTAF(II)68. It contains a consen sus RNA-binding domain (RNP-CS) and binds not only RNA, but also singl e stranded (ss) DNA, hTAF(II)68 shares extensive sequence similarity w ith TLS/FUS and EWS, two human nuclear RNA-binding prooncoproteins whi ch are products of genes commonly translocated in human sarcomas, Like hTAF(II)68, TLS/FUS is also associated with a sub-population of TFIID complexes chromatographically separable from those containing hTAF(II )68. Therefore, these RNA and/or ssDNA-binding proteins may play speci fic roles during transcription initiation at distinct promoters, Moreo ver, we demonstrate that hTAF(II)68 co-purifies also with the human RN A polymerase II and can enter the preinitiation complex together with Pol II.