Long non-coding RNAs (LncRNAs) are important regulators of gene transcription. My thesis work aims at gaining more insights into the molecular mechanism of PHO84 antisense RNA-mediated silencing. For this purpose, I used the synthetic genetic array (SGA) procedure and found, in addition to previously identified histone modifying enzymes, histone chaperones and chromatin remodelling complexes to be potential players of this mechanism. In the second part of my thesis, I discuss the results we published showing that the silencing of PHO84 gene could be induced in a trans-model independently of the gene position. Furthermore we show that the Set1 methyltransferase is a key player of this mechanism. In conclusion, all our data highlight the importance of non-coding RNAs in mediating RNAi independent transcriptional gene silencing.