The RNA polymerase II general transcription factor TFIID is a complex containing the TATA-binding protein (TBP) and associated factors (TAFs). We have used a mutant allele of the gene encoding yeast TAF II 68/61p to analyze its function in vivo. We provide biochemical and genetic evidence that the C-terminal ␣-helix of TAF II 68/61p is required for its direct interaction with TBP, the stable incorporation of TBP into the TFIID complex, the integrity of the TFIID complex, and the transcription of most genes in vivo. This is the first evidence that a yeast TAF II other than TAF II 145/130 interacts with TBP, and the implications of this on the interpretation of data obtained studying TAF II mutants in vivo are discussed. We have identified a high copy suppressor of the TAF68/61 mutation, TSG2, that has sequence similarity to a region of the SAGA subunit Ada1. We demonstrate that it directly interacts with TAF II 68/ 61p in vitro, is a component of TFIID, is required for the stability of the complex in vivo, and is necessary for the transcription of many yeast genes. On the basis of these functions, we propose that Tsg2/TAF II 48p is the histone 2A-like dimerization partner for the histone 2B-like TAF II 68/61p in the yeast TFIID complex.Initiation of RNA polymerase II transcription is regulated through the concerted actions of general transcription factors, which bind near the polymerase start site, and specific transcriptional activator proteins, which bind at more distant sites (1-3). Sequence-specific gene regulatory proteins are thought to target multiple components of the general transcriptional machinery by direct protein-protein interactions or through coactivator proteins (3-4). Much focus has been placed on TFIID, which is composed of the TATA-binding protein (TBP) 1 and a collection of tightly associated factors commonly referred to as TAF II s (4, 5). A plethora of biochemical analyses of mammalian and Drosophila TFIID indicates that TAF II s play a crucial role in promoter recognition and may be a target of some activator proteins (4, 5).The identification of yeast TAF II s (6, 7) and the subsequent analysis of mutants in vivo (8 -10) altered our understanding of the role of TAF II s in the regulation of transcription. Despite forming a discrete complex, mutation of different TAF II genes can have very different effects on the structure and function of the TFIID complex (11). Mutation or depletion of seven different yeast TAF II s failed to result in global changes in gene expression (8 -10, 12). Most notably, mutation or depletion of TAF II 145p, the dTAF II 250 homologue, affects only a small portion of the genome (9, 10, 12-14). In contrast, inactivation of temperature-sensitive mutants of yeast TAF68/61, TAF60, TAF40, TAF25, and TAF17 resulted in much broader transcriptional phenotypes (15)(16)(17)(18)(19)(20). The interpretation of the results obtained using TAF II mutants has been complicated by the presence of certain TAF II s in the SAGA histone acetyltransferase complex (21,22). It has been pr...

To determine sequence variations of the BUB1 and BUB1B genes in pancreatic cancer, the entire coding regions of the BUB1 and BUB1B genes were sequenced in pancreatic cancer cell lines and xenografts. Although only polymorphic alterations were found in the BUB1B gene, the aneuploid pancreatic cell line Hs766T had two novel missense variants

Certain samples of the cell line Hs766T within our laboratory were contaminated by the cell line RKO in the past. This affected two published papers (Hempen et al., 2002;Sohn et al., 2002 Sohn et al., , 2003. We recently identified that the reported BUB1 alteration is present in RKO cells and is not present in Hs766T cells. RKO cells are known to have an intact mitotic checkpoint (Cahill et al., 1998). Using current cell lines having identities confirmed by the sequencing of their other known mutant genes, we confirm the finding of a mitotic checkpoint defect among pancreatic cancers having CIN (chromosomal instability): the maximal mitotic index under colcemid (0.1 ug/ml) treatment is 85% for RKO cells (colorectal cancer, MSI, microsatellite instability), 9.4% for Hs766T cells (pancreatic, CIN), 23% for Su86.86 cells (pancreatic, CIN), and 44% for BxPC3 cells (pancreatic, CIN). The reported double missense mutation of the mitotic checkpoint BUB1 gene is thus associated not with a defective mitotic checkpoint in a CIN line as we had reported, but interestingly occurs in an MSI line having an intact checkpoint. The prevalence rate of BUB1 and other mitotic checkpoint gene mutations in MSI cell lines has not yet been reported. Presumably, BUB1 missense mutations do not always create a significant functional defect.The authors regret the error and any inconvenience caused. REFERENCES