NORMAL GENOMIC

• Basu A, Dong B, Krainer AR, Howe CC
• The intracisternal A-particle proximal enhancer-binding protein activates transcription and is identical to the RNA- and DNA-binding protein p54nrb/NonO.
• Mol Cell Biol. 1997; 17: 677-86
• Display abstract

• The long terminal repeats of murine intracisternal A particles (IAPs) contain an IAP proximal enhancer (IPE) element that is inactive in murine F9 embryonal carcinoma cells and active in the parietal endoderm cell line PYS-2. The element binds efficiently to a 60-kDa IPE-binding protein (IPEB) present in PYS-2 cells but poorly to F9 proteins, suggesting a role for IPEB in regulating IAP expression. We have purified calf thymus IPEB, which binds to the IPE and transactivates a reporter gene in HeLa cell extracts. Based on the peptide sequence of the purified calf IPEB, we have cloned a 420-bp cDNA and showed that the encoded protein is the homolog of human p54nrb and mouse NonO, which are characterized by the presence of two RNA recognition motifs. We show that p54nrb is an IPE-binding transcription activator with its DNA-binding and activation domains in the N- and C-terminal halves, respectively. The activation domain of p54nrb is active in HeLa, PYS-2, and F9 cells, whereas p54nrb as a whole molecule is active in HeLa and PYS-2 cells but not in F9 cells. Thus, the lack of activity of p54nrb in F9 cells is due to an ineffective DNA-binding domain. We demonstrate that p54nrb also binds to a pre-mRNA. Based on the close sequence relatedness of this protein to PSF, which is required for pre-mRNA splicing in vitro, we discuss the possibility that p54nrb has dual roles in transcription and splicing.

• Huang SH, Qin CH
• [A novel family of transcription factors: signal transducers and activators of transcription]
• Sheng Li Ke Xue Jin Zhan. 1997; 28: 145-7

• Dikstein R, Zhou S, Tjian R
• Human TAFII 105 is a cell type-specific TFIID subunit related to hTAFII130.
• Cell. 1996; 87: 137-46
• Display abstract

• We previously characterized Drosophila and human TAF subunits that make up the core TFIID complex found in all cells. Here, we report that differentiated B cells contain a novel substoichiometric TAF of 105 kDa not found associated with TFIID isolated from other cell types. The cDNA encoding hTAFII105 reveals a highly conserved C-terminal domain shared by hTAFII130 and oTAFII110, while the N-terminal coactivator domain has diverged significantly. All cells tested express TAFII105 mRNA, but only B cells contain significant levels of protein associated with TFIID. Transient overexpression of hTAFII105 selectively squelches the transcription of some genes in B cells. These properties suggest that TAFII105 is a cell type-specific subunit of TFIID that may be responsible for mediating transcription by a subset of activators in B cells.