EXPRESSION OF A MHC NON‐CLASSICAL CLASS I GENE, 04, 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, β‐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.