EXPRESSION OF A MHC NONCLASSICAL CLASS-I GENE, Q4, IS SIMILAR TO A CLASSICAL CLASS-I GENE, D(P)

We have investigated the effects of the cell cycle on expression of Q4 mRNA. Q4, the gene encoding the Qb-1 antigen, is transcribed in a wide variety of tissues, unlike many other non-classical class I genes. We have compared the pattern of Q4 transcription in the cell cycle to classical class I, beta-2-microglobulin and actin. We found that the pattern of Q4 RNA levels resembles that of the classical class I genes, consistent with the similarity of the 5' sequences of Q4 and K/D. Thus, Q4 mRNA accumulates during the cell cycle along with the total RNA, but does not show specific transcriptional enhancement. This is consistent with a function for Q4 similar to the classical K/D gene products.