CYCLIC-AMP SIGNALING IS REQUIRED FOR FUNCTION OF THE N-TERMINAL AND CR-1 DOMAINS OF ADENOVIRUS E1A IN SACCHAROMYCES-CEREVISIAE

We have constructed yeast vectors in which derivatives of the adenovir us E1A gene are expressed from the GAL1 promoter. Cells expressing E1A (289) grow poorly and accumulate cells with a 1C DNA content. Using a series of E1A deletion mutants, we have identified three regions withi n the E1A protein that are necessary for the G(1) growth phenotype; ea ch deletion partially relieves the growth defect. These deletions span residues 4-25, 38-60 and 140-186, which fall within the N-terminal, C R1 and CR3 domains of E1A respectively. Expression of the first 82 res idues of E1A, spanning just the N-terminal and CR1 domains, strongly i nhibits yeast cell growth in G(1) showing that these domains can funct ion independently of other domains of E1A. Using this strong growth in hibition, we isolated a yeast mutant in the net1 gene that conferred r esistance to the expression of E1A(1-82). The mutant was insensitive t o expression of both E1A(1-82) and full length E1A, but remained sensi tive to the toxicity caused by over-expression of a Ga14p-VP16 fusion. Finally, we found that the function of E1A in yeast depends on the cy clic AMP signaling pathway, providing a striking parallel with the act ion of E1A at the c-fos promoter in mammalian cells. These results sug gest that a genetic analysis of the yeast model system will provide re levant new insights into mechanisms of gene regulation by E1A proteins .