Peer review process
Revised: This Reviewed Preprint has been revised by the authors in response to the previous round of peer review; the eLife assessment and the public reviews have been updated where necessary by the editors and peer reviewers.
Read more about eLife’s peer review process.Editors
- Reviewing EditorPablo ManavellaUniversidad Nacional del Litoral-CONICET, Santa Fe, Argentina
- Senior EditorBenoît KornmannUniversity of Oxford, Oxford, United Kingdom
Reviewer #1 (Public Review):
Here, Ensinck et al. investigated the composition of the yeast mRNA m6A methyltransferase complex required for meiosis. This complex was known to contain three proteins, but is much more complex in mammals, insects and plants. Through IP-MS analysis they identified three more proteins Kar4, Ygl036w and Dyn2. Of these Kar4 and Ygl036w are homologous to Mettl14 and Virma, respectively, and, like the previously described factors are essential for m6A deposition, mating and binding of the reader Pho92 to mRNA during meiosis by evidence acquired with appropriate methodology. Dyn2 is a novel factor not described for any m6A complex and is not essential for m6A deposition, mating and binding of the reader Pho92 to mRNA during meiosis.
In addition, detailed analysis of the Slz1 revealed homology to the mammalian factor m6A complex member ZC3H13 to comprise a conserved complex of five proteins, Mettl3, Mettl14, Mum2/WTAP, Virma and Slz/ZC3H13. When co-expressed in insects cells, they co-purify stoichiometrically and presence of Mum2 as a dimer is also indicated as shown for WTAP.
Complementary to these data they show that stability of the individual complex members is affected in mutants supporting that they are stabilized through complex formation.
Furthermore, the authors then show that kar4 has additional roles in mating that is separable from its role through the m6A complex in meiosis.
The authors employ appropriate methodology throughout to address their aims and present convincing evidence for their claims. The evidence presented here reinforces that the m6A complex is evolutionary highly conserved which has broad scope for its functional analysis in humans and model organisms.
Reviewer #2 (Public Review):
N6-methyladenosine (m6A), the most abundant mRNA modification, is deposited by the m6A methyltransferase complexes (MTC). While MTC in mammals/flies/plants consists of at least six subunits, yeast MTC was known to contain only three proteins. Ensinck, Maman, et al. revisited this question using a proteomic approach and uncovered three new yeast MTC components, Kar4/Ygl036w/Dyn2. By applying sequence and structure comparisons, they identified Kar4, Ygl036w, Slz1 as homologs of the mammalian METTL14, VIRMA. ZC3H13, respectively. While these proteins are essential for m6A deposition, the dynein light chain protein, Dyn2, is not involved in mRNA methylation. Interestingly, while mammalian and fly MTCs are configured as MAC (METTL3 and METTL14) and MACOM (other subunits) complexes, yeast MTC subunits appear to have different configurations. Finally, Kar4 has a different role as transcription regulator in mating, which is not mediated by other MTC members. These data establish fundamental framework for the yeast MTC and also provide novel insights for those studying m6A deposition.