Mechanisms of nitrogen catabolite repression-sensitive gene regulation by the GATA transcription factors in Saccharomyces cerevisiae

binding of specific transcription factors to DNA. A global understanding of the mechanisms of gene

transcriptional regulation of Saccharomyces cerevisiae goes through the description of the targets and

the behavior of those transcription factors.

The GATA factors are specific transcription factors intervening in the regulation of Nitrogen

Catabolite Repression (NCR)-sensitive genes, a mechanism encompassing the transcriptional

regulations leading to the preferential use of good nitrogen sources of the growth medium of yeast in

the presence of less good nitrogen sources. Those 4 GATA factors involved in NCR comprise 2

activators (Gat1 and Gln3) and 2 repressors (Gzf3 and Dal80).

Generally speaking, the promoters of genes have always been described like the main place for

the integration of the transcription regulation signals relayed by the general and specific transcription

factors and the chromatin remodeling factors. Furthermore, the GATA factors have been described as

integrating the external signals of nitrogen availability thanks to their specific DNA binding to

consensus GATA sequences in the promoter of NCR-sensitive genes. The results presented here

introduce many nuances to the model, notably implying new proteins but also new regions in the

regulation process of the NCR-sensitive gene regulation. Indeed, the first goal of this work is to

discover and understand the mechanisms of NCR-sensitive gene regulation that will explain the

variations in their expression levels in the presence of various nitrogen sources and their dependency

towards the GATA factors.

Strikingly, it appeared that GATA factor positioning was not limited to the promoter, but

occurred also in the transcribed region. It seems that the transcription factors may have been driven

by the general transcription machinery (Pol II). The binding of a chromatin remodeling complex, RSC,

has also been demonstrated in the coding region of NCR-sensitive genes. Moreover, the binding of the

histone acetyltransferase complex, SAGA, recruited by the GATA activators, was highlighted along

NCR-sensitive genes. The SAGA complex was also implied in their transcriptional regulation.

Finally, a ChIP-sequencing experiment revealed an unsuspected number and diversification of

targets of the GATA factors in yeast, which were not limited to NCR-sensitive genes.