Human Ia-associated invariant chain gene has multiple transcription initiation sites in CLL cells

We show a northern transfer experiment revealed two mRNA of Ia-associated invariant chain (In) gene in chronic lymphocytic leukemia (CLL) cells which are approximately 1580 and 1440 nucleotides in length. Primer extension experiment shows that less prominent transcript was found to initiate 140 nucleotides upstream from the major cap site. The newly identified cap site was preceded by CG rich sequence but no typical promotor sequence. Southern hybridization analysis with In cDNA probe indicates no recombination or amplification of In gene in the CLL cells. This is the first documented example of such a mode of expression in malignant cells in vivo.