Features of the two gene pairs RD-SKI2W and DOM3Z-RP1 located between complement component genes factor B and C4 at the MHC class III region

Located at the 30 kb genomic region between complement factor B and compone nt C4 are four ubiquitously expressed genes RD, SKI2W, DOM3Z and RP1. Besid es RP1, the protein products of the other three genes each has highly conse rved homologues or related proteins in lower eukaryotes, contains leucine z ipper motifs for protein interaction, and plays important roles related to RNA metabolism. RD is a subunit of the negative transcription elongation fa ctor, critical for the regulation of gene expression. It has an RNA recogni tion motif and 24 copies of Arg-Asp (RD) repeats. Ski2w is a nucleolar and cytoplasmic protein that has a putative RNA helicase domain. Fusion protein s of human Ski2w expressed in insect cells and bacteria have ATPase activit y. The cytoplasmic protein of human Ski2w is associated with the polysomes and probably the 40S subunit of ribosomes. Ski2w is probably involved in th e regulation of translation and RNA turnover. Dom3z is a nuclear protein wh ose yeast homologue forms a complex with an exoribonuclease. RP1 (or STK19) is a Ser/Thr nuclear protein kinase. No homologues of RP1 in lower eukaryo tes have been discovered. Six polymorphic residues are present in human Ski 2w and two in Dom3z. The potential roles of Ski2w and Dom3z on the clearanc e of degraded nuclear and cytoplasmic RNA raised their possibilities as sus ceptibility genes of systemic lupus erythematosus that is a disease with fl awed processes in the removal of apoptotic materials.