cDNA clones to human
prepro-gastrin-releasing peptide (
prepro-GRP)
mRNA detect synthesis of
prepro-GRP-related transcripts in 4 of 7
small cell lung cancer (SCLC) cell lines and 1 of 2 metastatic SCLC
tumors examined. A correlation is noted between
prepro-GRP gene expression and the occurrence of
bombesin-related immunoreactivity in SCLC cell lines. Examination of the structure of
prepro-GRP transcripts found in SCLC reveals three types of
prepro-GRP mRNA which differ in the structure of a putative GRP-associated
peptide in the pro-GRP precursor. The subcellular distribution of
prepro-GRP-related RNAs and structure of SCLC-derived
prepro-GRP cDNA clones suggest that all three types of transcript could function as mRNAs, although there are differences in the prevalence of the different
RNA types in different cellular compartments. Comparison of the sequence of
cDNA clones with the sequence of a genomic
prepro-GRP clone reveals that the three forms of
prepro-GRP mRNA arise from a single primary transcript which undergoes alternative processing from two
splice donor sites to two
splice acceptor sites. The predicted amino acid sequence of the translated products of the three mRNAs are quite distinct, leading to predicted pro-GRP molecules of differing structure.