SPT5, an Essential Gene Important for Normal Transcription in Saccharomyces cerevisiae, Encodes an Acidic Nuclear Protein with a Carboxy-Terminal Repeat

Abstract

Mutations in the SPT5 gene of Saccharomyces cerevisiae were isolated previously as suppressors of delta insertion mutations at HIS4 and LYS2. In this study we have shown that spt5 mutations suppress the his4-912 delta and lys2-128 delta alleles by altering transcription. We cloned the SPT5 gene and found that either an increase or a decrease in the copy number of the wild-type SPT5 gene caused an Spt- phenotype. Construction and analysis of an spt5 null mutation demonstrated that SPT5 is essential for growth, suggesting that SPT5 may be required for normal transcription of a large number of genes. The SPT5 DNA sequence was determined; it predicted a 116-kDa protein with an extremely acidic amino terminus and a novel six-amino-acid repeat at the carboxy terminus (consensus = S-T/A-W-G-G-A/Q). By indirect immunofluorescence microscopy we showed that a bifunctional SPT5-beta-galactosidase protein was located in the yeast nucleus. This molecular analysis of the SPT5 gene revealed a number of interesting similarities to the previously characterized SPT6 gene of S. cerevisiae. These results suggest that SPT5 and SPT6 act in a related fashion to influence essential transcriptional processes in S. cerevisiae.

The pleiotropic roles of SPT5 in transcription

“…SPT5 function in productive transcription was already established by a host of studies in yeast, which lacks a pervasive pausing phenotype and thus is an ideal model to evaluate regulation of processivity by SPT5. In S. cerevisiae, Spt5 is required to sustain global transcription and cell survival, with its mutation or depletion leading to a genome-wide defect in Pol II progression in gene bodies [ 2 , 81 , 87 , 88 ]. Consistently, a vast majority of genes are downregulated at levels of both nascent and mature RNAs upon SPT5 depletion in Drosophila [ 89 ].…”

TheSaccharomyces cerevisiaeCdc68 Transcription Activator Is Antagonized by San1, a Protein Implicated in Transcriptional Silencing

“…Several other proteins have been implicated in widespread transcriptional regulation: Spt2/Sinl (an HMG1-like protein [28]), members of the histone group of Spt proteins, including Spt4, Spt5, and Spt6 (8,33,61,62,65), and a global transcription regulator, Sin4 (23), have been postulated to regulate transcription by remodeling chromatin structure.…”

“…The 8 insertions at these two loci have previously been shown to alter transcription and thereby cause a Hisor Lys-phenotype (59,66). All spt mutations that have been reported, including cdc68/ sptl6 mutations, suppress these 8 insertions by altering transcription initiation (8,9,32,61). The identification of CDC68 as an SPT gene provides further evidence that the Cdc68 protein plays an essential role in transcription.…”

A conserved function of corepressors is to nucleate assembly of the transcriptional preinitiation complex

“…TPLN188 interacted with SPT4 through its LisH domain (Figure 3, 4A), and we hypothesized that it was through this interaction that it controls the activity of the SPT complex containing SPT4, SPT5 and SPT6. SPT5 and SPT6 loss of function mutants are lethal in yeast 50,51 , and the point mutations spt5-194 (S324F 48 ) and spt6-14 (S952F 33 ) we identified in the R-SGA screen library are temperature sensitive alleles. To test the requirement for SPT4, SPT5 and SPT6 in maintaining repression of a TPLrepressed promoter, we used the Anchor Away 52 system for inducible protein depletion from the nucleus (Figure 4B) and combined it with quantification of transcriptional activity at the synthetic locus in the SPARC (Figure 2A).…”