BACKGROUND: Gene expression is achieved by the coordinated action of multiple 
factors to ensure a perfect synchrony from chromatin epigenetic regulation 
through to mRNA export. Sus1 is a conserved mRNA export/transcription factor and 
is a key player in coupling transcription initiation, elongation and mRNA 
export. In the nucleus, Sus1 is associated to the transcriptional co-activator 
SAGA and to the NPC associated complex termed TREX2/THSC. Through these 
associations, Sus1 mediates the nuclear dynamics of different gene loci and 
facilitate the export of the new transcripts.
RESULTS: In this study, we have investigated whether the yeast Sus1 protein is 
linked to factors involved in mRNA degradation pathways. We provide evidence for 
genetic interactions between SUS1 and genes coding for components of P-bodies 
such as PAT1, LSM1, LSM6 and DHH1. We demonstrate that SUS1 deletion is 
synthetic lethal with 5'-->3' decay machinery components LSM1 and PAT1 and has a 
strong genetic interaction with LSM6 and DHH1. Interestingly, Sus1 
overexpression led to an accumulation of Sus1 in cytoplasmic granules, which can 
co-localise with components of P-bodies and stress granules. In addition, we 
have identified novel physical interactions between Sus1 and factors associated 
to P-bodies/stress granules. Finally, absence of LSM1 and PAT1 slightly promotes 
the Sus1-TREX2 association.
CONCLUSIONS: In this study, we found genetic and biochemical association between 
Sus1 and components responsible for cytoplasmic mRNA metabolism. Moreover, Sus1 
accumulates in discrete cytoplasmic granules, which partially co-localise with 
P-bodies and stress granules under specific conditions. These interactions 
suggest a role for Sus1 in gene expression during cytoplasmic mRNA metabolism in 
addition to its nuclear function.