Regulation of APG14 expression by the GATA-type transcription factor Gln3p

Gln3p is a nitrogen catabolite repression-sensitive GATA-type transcription factor. Its nuclear accumulation was recently shown to be under the contro l of TOR signaling. Gln3p normally resides in the cytoplasm. When cells are starved from nitrogen nutrients or treated with rapamycin, however, Gln3p becomes translocated into the nucleus, thereby activating the expression of genes involved in nitrogen utilization and transport. To identify other ge nes under the control of Gln3p, we searched for the Gln3p-binding GATAA mot ifs within 500 base pairs of the promoter sequences upstream of the yeast o pen reading frames in the Saccharomyces Genome Database. APG14 a gene essen tial for autophagy, was found to have the most GATAA motifs. We show that n itrogen starvation or rapamycin treatment rap idly causes a more than 20-fo ld induction of APG14. The expression of APG14 is dependent on Gln3p; delet ion of Gln3p severely reduced its induction by rapamycin, whereas depletion of Ure2p caused its constitutive expression. However, overexpression of AP G14 led to only a slight increase in autophagy in nitrogen rich medium. The refore, these results define a signaling cascade leading to the expression of APG14 in response to the availability of nitrogen nutrients and suggest that the regulated expression of APG14 contributes to but is not sufficient for the control of autophagy.