GZF3P, A 4TH-GATA FACTOR INVOLVED IN NITROGEN-REGULATED TRANSCRIPTIONIN SACCHAROMYCES-CEREVISIAE

In Saccharomyces cerevisiae, two positive transcription factors of the GATA family, Gln3p and Nil1p/Gat1p, upregulate the expression of mult iple nitrogen pathway genes via upstream 5'-GATA-3' sequences. Another GATA factor, Uga43p/Dal80p, downregulates to varying degrees the expr ession of some nitrogen-regulated genes. Here, we report the functiona l analysis of a fourth GATA factor, Gzf3p/Nil2p, whose gene was discov ered by systematic sequencing of chromosome X. The Gzf3 protein most c losely resembles Uga43p. Similar to Uga43p, Gzf3p has the properties o f a negative GATA factor. While Uga43p is active specifically under ni trogen-derepression conditions, Gzf3p exerts its negative regulatory f unction specifically on preferred nitrogen sources: it is involved in nitrogen repression of Nil1p-dependent transcription. At least one pos itive GATA factor is required for the UGA43 and GZF3 genes to be expre ssed. The Uga43p factor negatively regulates GZF3 expression and vice versa. In addition, both Uga43p and Gzf3p moderately regulate expressi on of their own genes. These two proteins seem to be parts of a comple x network of GATA factors which probably play a determining role in ni trogen-regulated transcription.