The m6A methyltransferase Ime4 epitranscriptionally regulates triacylglycerol metabolism and vacuolar morphology in haploid yeast cells.

N6-Methyladenosine (m6A) is among the most common modifications
in eukaryotic mRNA. The role of yeast m6A methyltransferase,
Ime4, in meiosis and sporulation in diploid strains is very
well studied, but its role in haploid strains has remained unknown.
Here, with the help of an immunoblotting strategy and Ime4-GFP
protein localization studies, we establish the physiological role of
Ime4 in haploid cells.Ourdata showed that Ime4 epitranscriptionally
regulates triacylglycerol metabolism and vacuolar morphology
through the long-chain fatty acyl-CoA synthetase Faa1, independently
of the RNA methylation complex (MIS complex). The MIS
complex consists of the Ime4, Mum2, and Slz1 proteins. Our affinity
enrichment strategy (methylated RNA immunoprecipitation
assays) using m6A polyclonal antibodies coupled with mRNA isolation,
quantitative real-timePCR,andstandardPCRanalyses confirmed
the presence ofm6A-modified FAA1 transcripts in haploid
yeast cells. The term “epitranscriptional regulation” encompasses
theRNAmodification-mediated regulation of genes. Moreover,we
demonstrate that the Aft2 transcription factor up-regulates FAA1
expression. Because them6Amethylation machinery is fundamentally
conserved throughout eukaryotes, our findings will help
advance the rapidly emerging field ofRNAepitranscriptomics.The
metabolic link identified here betweenm6A methylation and triacylglycerol
metabolism via the Ime4 protein provides new insights
into lipid metabolism and the pathophysiology of lipid-related
metabolic disorders, such as obesity. Because the yeast vacuole isan
analogue of the mammalian lysosome, our findings pave the way to
better understand the role ofm6Amethylation in lysosome-related
functions and diseases.