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SAGA/TFTC, which is a histone acetyltransferase complex, plays an important role in the regulation of transcription. We have identified that the metazoan TFTC/STAGA complexes had histone H2A and H2B deubiquitinase activity that is carried out by a DUBm (deubiquitination module). We studied the DUBm of SAGA in Drosophila melanogaster and identified Drosophila homologs of yeast DUBm components. Two subunits of DUBm (Sus1/ENY2 and Sgf11) were shown to have functions separate from DUBm function. Thus, Sus1/ENY2 was shown to be present in several different complexes. Sgf11 was found to be associated with the cap-binding complex (CBC) and recruited onto growing messenger ribonucleic acid (mRNA). Also, we have shown that Sgf11 interacted with the TREX-2/AMEX mRNA export complex and was essential for mRNA export from the nucleus. Immunostaining of the polytene chromosomes of Drosophila larvae revealed that Sgf11 is present at the sites of localization of snRNA genes. It was also found in immunostaining experiments that dPbp45, the subunit of the PBP complex, the key player in the snRNA transcription process, is associated not only with the snRNA gene localization sites, but with other sites of active transcription by PolII. We also revealed that Sgf11 was present at many active transcription sites in interbands and puffs on polytene chromosomes, Sgf11 was localized at all Brf1 (the component of the RNA polymerase III basal transcription complex) sites. We concluded that SAGA coactivated transcription of both the PolII and PolIII-dependent snRNA genes.

SAGA is a histone acetyltransferase complex that cotranscriptionally performs histone modifications and is implicated in the regulation of gene expression at the level of changes in chromatin structure. SAGA is also involved in mRNP biogenesis and export. In this review, we examined the contribution of SAGA and its subunits to development. We also discuss the diseases associated with impaired activity of SAGA subunits. [ABSTRACT FROM AUTHOR]

Eukaryotic gene expression is a multistep process of high complexity. Transcription is one of the cardinal and tightly regulated phases of gene expression. To provide accurate and precise work of the gene regulation apparatus, including a plethora of modifications of the chromatin structure and nucleosome, dynamic turnover must take place. All transcription steps are under the control of large multiprotein coactivator complexes. In this review, we discuss the evolutionary conservative SAGA complex, which acetylates and deubiquitinates histones during transcription activation and, furthermore, is involved in subsequent stages of mRNP biogenesis and export. [ABSTRACT FROM AUTHOR]