TRANSCRIPTION OF THE MURINE CLASS-II EB GENE IS REGULATED PRIMARILY AT THE LEVEL OF TRANSCRIPTIONAL INITIATION

The constitutive and inducible expression of MHC class II genes is kno wn to be regulated by multiple upstream promoter elements. Transient t ransfection assays implicate the proximal promoter region as both nece ssary and sufficient for appropriate tissue-specific and inducible exp ression. However, transgenic mouse experiments suggest that additional control regions are important. In this study we tested the hypothesis that additional regulation of class II expression occurred at the lev el of RNA polymerase II elongation. Nuclear run-on analysis using sing le-stranded probes spanning the entire Eb gene was performed on a vari ety of class II-positive, class II-negative, and class II-inducible ce ll lines. The results demonstrate that, while there is not an even dis tribution of RNA polymerase along the gene, there is no evidence for a regulated block in elongation. These data further support the idea th at the primary mechanism of class II gene regulation is at the level o f transcriptional initiation. (C) 1994 Academic Press, Inc.