The nucleus stores the genetic information in a well-organized manner to ensure its transmission at every cell division. This process relies on several interconnected steps: transcription and processing of the pre-mRNA, export of mRNA into the cytoplasm and translation into a functional protein. During my doctoral studies I focused my attention on the fundamental step of mRNA export into the cytoplasm using Saccharomyces cerevisiae as a model organism. mRNA export starts during transcription, when export factors are recruited in a RNA polymerase II dependent manner. All mRNAs are exported by the export receptor Mex67. Several adaptors help Mex67 accomplishing this task. The first identified adaptor is the essential protein Yra1 (Aly/REF in mammals), which interacts both with RNAs and Mex67. Throughout the course of my thesis I concentrated my studies on Yra1 to further characterize its role as an mRNA export adaptor and to elucidate the mechanisms regulating its expression.