Isolation of cDNA clones and tissue expression of rat ral A and ral B GTP-binding proteins.

cDNA clones encoding the low molecular weight GTP-binding proteins ral A (951 bp) and ral B (2073 bp), including the entire coding region (618 bp), were isolated from a rat PC12 pheochromocytoma library. Northern analyses demonstrated that both ral A and ral B are widely expressed in rat tissues. Two ral A transcripts of 1.1 and 2.9 kb were observed in most tissues in varying proportions. The 1.1 kb ral A band of testes was further shown to be composed of two closely migrating species. In contrast to these findings, a single ral B transcript of 2.3 kb was detected in most tissues. Steady-state levels of ral A transcripts appear greater than ral B. Quantitatively, the testes exhibited the highest ral A and ral B mRNA levels, with lower levels observed in the brain, adrenal and pituitary glands, kidney and ovary. Ral mRNA levels were lowest in muscle tissue, particularly skeletal muscle.