Hoffmann R, Grabinska K, Guan Z, Sessa WC, Neiman AM

Dolichols are isoprenoid lipids of varying length that act as sugar carriers in glycosylation reactions in the endoplasmic reticulum. InSaccharomyces cerevisiae, there are twocis-prenyltransferases that synthesize polyprenol-an essential precursor to dolichol. These enzymes are heterodimers composed of Nus1 and either Rer2 or Srt1. Rer2-Nus1 and Srt1-Nus1 can both generate dolichol ...

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in vegetative cells, butsrt1∆ cells grow normally whilerer2∆ grows very slowly, indicating that Rer2-Nus1 is the primary enzyme used in mitotically dividing cells. In contrast,SRT1performs an important function in sporulating cells, where the haploid genomes created by meiosis are packaged into spores. The spore wall is a multilaminar structure andSRT1is required for the generation of the outer chitosan and dityrosine layers of the spore wall. Srt1 specifically localizes to lipid droplets associated with spore walls, and, during sporulation there is anSRT1-dependent increase in long-chain polyprenols and dolichols in these lipid droplets. Synthesis of chitin by Chs3, the chitin synthase responsible for chitosan layer formation, is dependent on thecis-prenyltransferase activity of Srt1, indicating that polyprenols are necessary to coordinate assembly of the spore wall layers. This work shows that a developmentally regulatedcis-prenyltransferase can produce polyprenols that function in cellular processes besides protein glycosylation.

Date: Dec. 01, 2017

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