ASYMMETRICAL LOCALIZATION OF MESSENGER-RNAS IN ENTEROCYTES OF HUMAN JEJUNUM

Intracellular localization of specific mRNAs is known to be a mechanis m for targeting proteins to specific sites within the cell. Previous s tudies from this laboratory have demonstrated co-localization of mRNAs and proteins for a number of genes in absorptive enterocytes of fetal rat intestine. The present study was undertaken to examine in human e nterocytes the intracellular localization patterns of mRNAs for the mi crovillous membrane proteins lactase-phlorizin hydrolase (LPH), sucras e-isomaltase (SI), and intestinal alkaline phosphatase (IAP), and the cytoskeletal protein beta-actin. In sections of human jejunum, mRNAs w ere localized by in situ hybridization using digoxigenin-labeled antis ense RNA probes. Both LPH and SI mRNAs were localized to the apical re gion of villous enterocytes, whereas IAP and beta-actin mRNAs were det ected both apically and basally relative to the nucleus. Therefore, in contrast to LPH, SI, and beta-actin mRNAs, which co-localize with the ir encoded proteins, that of IAP is present in the basal region of the cell where IAP protein has not directly been demonstrated to be prese nt. Absorptive enterocytes from humans possess the mechanisms for intr acellular mRNA localization, but not all mRNAs co-localize with their encoded proteins.