Polycistronic transcripts, where a single mRNA can encode several different polypeptide chains, are common in prokaryotes. In humans, only 3 bicistronic transcripts have been characterised to date. Human cDNAs encoding both RPP14 of the RNase P complex and mitochondrial 3-hydroxyacyl thioester dehydratase (HTD2) have been isolated. HTD2 functions in the mitochondrial fatty acid synthesis (FAS) pathway, dehydrating (3R)-hydroxyacyl-CoA (3HA-CoA) to trans-2-enoyl-CoA (t2E-CoA) (Autio et al. 2008).