Anne-Ruxandra Carvunis, University of Pittsburgh

Title: Change and Innovation in Biological Systems

Abstract: What makes each species unique? My research aims to understand how changes in DNA sequences translate into the evolution of phenotypes. In this seminar I will focus on a special case where mutations in non-genic sequences give rise to novel, species-specific, protein-coding genes: de novo gene birth. Protein-coding genes are thought to emerge de novo when non-genic sequences become transcribed, acquire open reading frames, and the corresponding non-genic transcripts access the translation machinery. However, biochemistry predicts that the polypeptides resulting from such translation events should predominantly encode insignificant polypeptides rather than proteins with specific biological roles. It is hard to imagine how such polypeptides could drive species-specific adaptations. To resolve this conundrum, we have formalized a model according to which the translation of non-genic transcripts does not systematically produce de novo genes with adaptive impact, but rather yields transitory “proto-genes”. These proto-genes would provide the organism with adaptive potential by exposing genetic variations that are usually hidden in non-genic sequences. The majority would likely return to a non-genic state but a subset may evolve into de novo genes, for instance if their expression is beneficial to the organism. In support for this model, widespread translation of non-genic transcripts has recently been documented across numerous species. Whether these translation events really do carry adaptive potential has not yet been demonstrated. I will show experimental results confirming that expression of proto-genes is often beneficial in yeast and discuss future research directions.

Refreshments will be served in the Molecular Biology Building Atrium at 3:45 p.m.

Host: Anne-Ruxandra Carvunis