Yeast targets for mRNA methylation

Abstract

N6-Methyladenosine (m6A) is a modified base present in the mRNA of all higher eukaryotes and in Saccharomyces cerevisiae, where there is an increase in m6A levels during sporulation. The methyltransferase, Ime4, is responsible for this modification and has a role in the initiation of meiosis. However, neither the function, nor the extent of distribution of this nucleotide modification is established. We demonstrate that in S. cerevisiae, substantial levels of internal adenosine methylation are present in the GpA context in mRNA from sporulating cells, which is consistent with the preferred methylation consensus of higher eukaryotes. Based upon our quantification data, every second transcript could contain one m6A during meiosis. As methylation is distributed across all mRNA size ranges, it is likely that m6A is not limited to a small population of messages. We developed a new antibody based method for identifying m6A containing messages, and using this method the transcripts of three key, early regulators of meiosis, IME1, IME2 and IME4 itself, were identified as being methylated. The position of m6A in IME2 was narrowed down to a region in the 3′-end. Methylation of these and other targets suggests mechanisms by which IME4 could control developmental choices leading to meiosis.

Sporulation in the Budding Yeast Saccharomyces cerevisiae

“…Ime4, which was originally identified as required for efficient expression of IME1 (Shah and Clancy 1992), is homologous to mRNA N6-adenosine methyltransferase in higher cells. During sporulation, Ime4 mediates N6-adenosine methylation of bulk mRNA, including the IME1 and IME2 transcripts (Clancy et al 2002;Bodi et al 2010). These observations imply that methylation of IME1 (and IME2) transcripts may control their expression, though the responsible mechanism is not yet clear.…”

Recent Advancement in Methodology for Understanding Epigenetic Modifications

“…Other site of modification includes the oxygen of the 2'OH moiety, the carbon atom at position 2 and in adenosine, the carbon atoms at position 5 in pyrimidines [17]. The most abundant and common RNA modifications in some viruses and most eukaryotes is N6-methyladenosine (m6A) which accounts for more than 80% of total RNA methylation [18][19][20][21][22][23]. In addition, it is also found in rRNA, tRNA, and small nuclear RNA (snRNA) as well as various long non-coding RNA, such as Xist [24,25].…”

m6a RNA Methylation: The Implications for Health and Disease

“…Even more intriguingly, some miRNAs themselves contain a m 6 A recognition site which may represent a mechanism for their regulation [4]. The m 6 A modification has been demonstrated in a broad range of species including humans [5], mice [5], virii [6,7], yeast [8][9][10], bacteria [11] and plants [12]. The methylation reaction is catalysed by a conserved mechanism, based around a multi-component enzymatic complex [13] and counterbalanced by a series of demethylases [14].…”