Dom34 Links Translation to Protein O-mannosylation

Abstract

In eukaryotes, Dom34 upregulates translation by securing levels of activatable ribosomal subunits. We found that in the yeast Saccharomyces cerevisiae and the human fungal pathogen Candida albicans, Dom34 interacts genetically with Pmt1, a major isoform of protein O-mannosyltransferase. In C. albicans, lack of Dom34 exacerbated defective phenotypes of pmt1 mutants, while they were ameliorated by Dom34 overproduction that enhanced Pmt1 protein but not PMT1 transcript levels. Translational effects of Dom34 required the 5′-UTR of the PMT1 transcript, which bound recombinant Dom34 directly at a CA/AC-rich sequence and regulated in vitro translation. Polysomal profiling revealed that Dom34 stimulates general translation moderately, but that it is especially required for translation of transcripts encoding Pmt isoforms 1, 4 and 6. Because defective protein N- or O-glycosylation upregulates transcription of PMT genes, it appears that Dom34-mediated specific translational upregulation of the PMT transcripts optimizes cellular responses to glycostress. Its translational function as an RNA binding protein acting at the 5′-UTR of specific transcripts adds another facet to the known ribosome-releasing functions of Dom34 at the 3′-UTR of transcripts.

The 5′ Untranslated Region of the EFG1 Transcript Promotes Its Translation To Regulate Hyphal Morphogenesis in Candida albicans

“…For example, unwinding of RNA structures by binding of helicase eIF4A to the 5′ UTR has been reported elsewhere ( 50 ). In C. albicans , the Dom34 protein, a predicted component of the no-go transcript degradation pathway, was found to bind to the 5′ UTR of transcripts encoding protein O-mannosyltransferases and to promote their translation ( 36 ). Binding proteins could also have an inhibitory function, such as the Rim4 protein in the yeast S. cerevisiae that binds to the 5′ UTR of the CLB3 transcript to inhibit its translation ( 51 ).…”

“…In addition, 5′ UTR sequences may contain binding sites for binding proteins that facilitate localization ( 35 ) and potentially translation of transcripts. In C. albicans , the Dom34 protein, known for its general role in no-go decay of mRNAs, was also shown to bind the 5′ UTR of specific transcripts encoding Pmt-type mannosyl transferases and favor their translation ( 36 ). Similarly, the Ssd1 RNA binding protein may positively affect translation of specific sets of transcripts involved in cell wall integrity and polarized growth ( 37 , 38 ).…”

The 5’ untranslated region of theEFG1transcript promotes its translation to regulate hyphal morphogenesis inCandida albicans

“…This potential structure could also be the target of RNA binding proteins that stimulate translation. Recently, the C. albicans Dom34 protein, a predicted component of the no go transcript degradation pathway, was found to bind to the 5’ UTR of transcripts encoding protein O -mannosyltransferases and to promote their translation (35). Binding proteins could also have an inhibitory function, such as the Rim4 protein in the yeast S. cerevisiae that binds to the 5’ UTR of the CLB3 transcript to inhibit its translation (49).…”

“…For preparation of samples derived from cells following hyphal induction, exponentially growing cells were washed with 1 X PBS and resuspended in YP medium containing 10 % horse serum (pre-warmed at 37 °C) and incubated at 37 °C for 15 min. Preparation of cells for polysome gradients was performed as described previously (35, 56), with some modifications. A portion of the culture (80 ml) was recovered and chilled for 5 min on ice in the presence of 0.1 mg/ml cycloheximide (CHX).…”

“…In addition, 5’ UTR sequences may contain binding sites for binding proteins that facilitate localization (34) and potentially translation of transcripts. In C. albicans , the Dom34 protein, known for its general role in no go decay of mRNAs, was also shown to bind the 5’ UTR of specific transcripts encoding Pmt-type mannosyl transferases and favour their translation (35). Similarly, the Ssd1 RNA binding protein may positively affect translation of specific sets of transcripts involved in cell wall integrity and polarized growth (36, 37).…”