The processed gene L32′, a member of the mouse gene family for ribosomal protein L32, could encode a 135 amino acid protein nearly identical to L32. The 5′-flanking region of the gene contains CAAT and TATA sites at positions commonly found in expressed genes. The L32′ gene lies within highly methylated, DNase I-insensitive chromatin of mouse L1210 cells. Although S1 nuclease digestion studies suggested that an L32′ transcript might be produced, an oligonucleotide probe specific for L32′ mRNA, and RNase digestion of a cRNA probe to L32′, indicated fewer than 0.1 L32′ transcripts/cell. These results demonstrate that extreme caution is required when measuring transcription from related genes.
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ACKNOWLEDGEMENTS We are grateful to Dr. Pam Mulligan for providing the lambda clone of the L32' gene, Drs. J. Larkin, R. Petersen and C. Hensel for useful discussions and reading the manuscript, Kris Kirkeby for artwork and Tina Lorsung for help with the manuscript. This research was supported by grant DMB-8405225 from the National Science Foundation.