The phylogenetic diversity of eukaryotic transcription.

Eukaryotic transcription is a highly regulated process involving interactions between large numbers of proteins. To analyse the phylogenetic distribution of the components of this process, six crown eukaryote group genomes were queried with a reference set of transcription-associated (TA) proteins. On average, one in 10 proteins encoded by these genomes were found to be homologous to sequences in the reference set. Analysis of families identified using an accurate sequence clustering algorithm and containing both TA proteins and eukaryotic sequences showed that in two-thirds of the families the homologues originate from a single kingdom. Furthermore, in only 15% of the fungal-specific clusters are the homologues present in both budding and fission yeast, as compared with the metazoan-specific clusters where 53% of the homologues originate from two or more species. Families whose members comprise general transcription factor or RNA polymerase subunits exhibit a low degree of taxon specificity, suggesting that the transcription initiation complex is highly conserved. This contrasts with transcriptional regulator families, that are primarily taxon-specific, indicating proteins controlling gene activation exhibit considerable sequence diversity across the eukaryotic domain.