Functional insights into the core-TFIIH from a comparative survey.

TFIIH is a eukaryotic complex composed of two subcomplexes, the CAK (Cdk activating kinase) and the core-TFIIH. The core-TFIIH, composed of seven subunits (XPB, XPD, P62, P52, P44, P34, and P8), plays a crucial role in transcription and repair. Here, we performed an extended sequence analysis to establish the accurate phylogenetic distribution of the core-TFIIH in 63 eukaryotic organisms. In spite of the high conservation of the seven subunits at the sequence and genomic levels, the non-enzymatic P8, P34, P52 and P62 are absent from one or a few unicellular species. To gain insight into their respective roles, we undertook a comparative genomic analysis of the whole proteome to identify the gene sets sharing similar presence/absence patterns. While little information was inferred for P8 and P62, our studies confirm the known role of P52 in repair and suggest for the first time the implication of the core TFIIH in mRNA splicing via P34.

Myotubularins, a large disease-associated family of cooperating catalytically active and inactive phosphoinositides phosphatases.

The myotubularin family is a large eukaryotic group within the tyrosine/dual-specificity phosphatase super-family (PTP/DSP). Among the 14 human members, three are mutated in genetic diseases: myotubular myopathy and two forms of Charcot-Marie-Tooth neuropathy. We present an analysis of the myotubularin family in sequenced genomes. The myotubularin family encompasses catalytically active and inactive phosphatases, and both classes are well conserved from nematode to man. Catalytically active myotubularins dephosphorylate phosphatidylinositol 3-phosphate (PtdIns3P) and PtdIns3,5P2, leading to the production of PtdIns and PtdIns5P. This activity may be modulated by direct interaction with catalytically inactive myotubularins. These phosphoinositides are signaling molecules that are notably involved in vacuolar transport and membrane trafficking. Myotubularins are thus proposed to be implicated in these cellular mechanisms, and recent observations on myotubularins homologues in the nematode Caenorhabditis elegans indicate a role in endocytosis.