Protein n-myristoylation affects proliferative potential during stationary phase in s. cerevisiae

The ability of various strains of S. cerevisiae to wiahstand nutrient deprivation, and other forms of induced stress, correlates with their inean lifespans. Protein N-myristoylation was used to test the hypothesis that factors required to maintain proliferative potential during stationary phase, a period of nutrient deprivation, may also regulate longevity. N-myristoyltransferase (Nmtlp) is essential for viability during log phase. S. cerevisiae contains 4 nonessential acylCoA synthetase genes (E4,I / E4A4) that are functionally interchangeable in log phase. Faalp and Faa4p account for >95% of myristoylCoA synthetase activity during exponential groxah. Studies using isogenic strains containing (i) Nmt lp or a conditional letlml mutant, umt451Dp with reduced affinity for myristoylCoA, and (ii) various combinalions of I,-L,I wild type or null alleles, revealed that introduction offaa4d into mnt1-451D cells resulted in a 10 reduction in colony forlning units 10-20 d after complete m, trient deprivation. No other combination offaaA allele xvtth X31T1 or mpltl- 4511) produced this phenotype. mt1-451Dfaa4A cells also have a dralnatically lower mean life-span compared to the wild type strain, as determined b. the number of buddings that they undergo on rich media. Stationary phase rant1-45 II)Jhad cells do not suffer a metabolic demise as judged by their ability to synthesize lipids and reduce metllylene blue. The stalionar3 phase phenoty,pe ofmntl-451Dfaad cells is rescued by NITI, I.1.14, I'Lll (phospholipase B). and TGLI (triglyccridc lipase). :V.WTI transcription is normally down-regulated upon entr) into stt|lionary phase, l' 1.-11 expression persists throughout log and stationary phase while Faa4p mRNA becomes undetectable after exit from log phase. These results implicate protein N-myristoylation as a regt, lalor of proliferative potential during log and stationar), phases.