Talk abstracts
Talk on Saturday 08:45-09:00am submitted by Kunal Chatterjee
Many commutes to work: species specific movement of intron-containing pre-tRNAs from nucleus to cytoplasm by multiple, parallel nuclear tRNA export pathways in yeast
Kunal Chatterjee (Molecular Genetics, The Ohio State University), Anita K.Hopper (Molecular Genetics,The Ohio State University)
Abstract:
In eukaryotic cells, tRNAs are exported out of the nucleus, their site of synthesis, to the cytoplasm, their site of function. We recently reported that the mRNA exporter Mex67-Mtr2 heterodimer co-functions with the canonical tRNA nuclear exporter Los1. Recent genetic and cytological data showed that Crm1, an exporter of proteins containing Leucine rich motif, also functions in tRNA nuclear export. We show that Crm1 is indeed a bonafide nuclear tRNA exporter as in vivo co-immunoprecipitation studies demonstrate that Crm1 co-purifies with tRNA. Moreover, like Mex67-Mtr2 and Los1, Crm1 exhibits substrate specificity for tRNA cargoes. Previous biochemical and structural studies documented that Los1 preferentially binds end-processed, appropriately structured tRNA. Therefore, Los1 also provides a tRNA quality control step, as it ensures tRNA end-processing prior to tRNA nuclear export. The tRNA structural features recognized by Mex67-Mtr2 and Crm1, and whether they participate in tRNA quality control, are unknown. Thus, we assessed the fidelity of the Los1-independent tRNA nuclear export pathways by three independent approaches and show these alternate pathways of tRNA nuclear export are error-prone. The question thus arises, why do cells employ multiple, parallel, but error-prone tRNA nuclear export pathways? We learned that environmental conditions can affect tRNA fidelity. For example, upon subjecting yeast to oxidative stress there is an increase in level of Mex67 and a concomitant elevated level of aberrant 5’-end extended tRNA. Thus, yeast seems to employ Los1-independent, error prone tRNA nuclear export pathways in varying environmental conditions, which may confer yet unknown selective advantages to cells.
Keywords: tRNA nuclear export, Yeast