Cotranslational assembly of the yeast SET1C histone methyltransferase complex

Abstract

While probing the role of RNA for the function of SET1C/COMPASS histone methyltransferase, we identified SET1RC (SET1 mRNA-associated complex), a complex that contains SET1 mRNA and Set1, Swd1, Spp1 and Shg1, four of the eight polypeptides that constitute SET1C. Characterization of SET1RC showed that SET1 mRNA binding did not require associated Swd1, Spp1 and Shg1 proteins or RNA recognition motifs present in Set1. RNA binding was not observed when Set1 protein and SET1 mRNA were derived from independent genes or when SET1 transcripts were restricted to the nucleus. Importantly, the protein-RNA interaction was sensitive to EDTA, to the translation elongation inhibitor puromycin and to the inhibition of translation initiation in prt1-1 mutants. Taken together, our results support the idea that SET1 mRNA binding was dependent on translation and that SET1RC assembled on nascent Set1 in a cotranslational manner. Moreover, we show that cellular accumulation of Set1 is limited by the availability of certain SET1C components, such as Swd1 and Swd3, and suggest that cotranslational protein interactions may exert an effect in the protection of nascent Set1 from degradation.

Widespread Cotranslational Formation of Protein Complexes

“…In this case, cotranslational assembly would stabilise the protein by reducing the time during which a protein is susceptible to degradation. This explanation has been proposed for the SET1C histone methyltransferase complex [7]. Consistently, Pcr1p is unstable in the absence Atf1p [24].…”

Quantitative Dissection and Stoichiometry Determination of the Human SET1/MLL Histone Methyltransferase Complexes

“…Csp15) is part of the yeast COMPASS complex. Shg1p interacts with RNA, which affects yeast SET1 complex assembly (55,56). Based on the identification of Bod1 in SET1B and the high sequence similarity, we propose that Bod1 and Bod1L1 are the higher eukaryotic paralogs of yeast Shg1p.…”

Co-translational assembly of protein complexes

“…Crucially, formation of the mRNA-associated sub-complex was found to be dependent on active translation, indicating that the subunits are binding to the nascent Set1p protein as it is translated. Furthermore, whereas structural data are not available for the full complex, it appears that the binding sites of Shg1p, Swd1p and Spp1p are localized to the N-terminal or central region of Set1p; this is consistent with co-translational assembly as these regions are translated earlier [33,34].…”

“…In work originally designed to investigate the role of mRNA in COMPASS function, a four-member sub-complex of COMPASS (formed by the proteins Swd1p, Spp1p, Shg1p and Set1p) was found to interact with SET1 mRNA [33]. Crucially, formation of the mRNA-associated sub-complex was found to be dependent on active translation, indicating that the subunits are binding to the nascent Set1p protein as it is translated.…”