“Relevance of the 3’ untranslated region (3’UTR) for regulation of expression of β1 integrin mRNAs”

ALBANA GATTELLI.; JONATHAN LAMARRE.; LUCIO H CASTILLA.; EDITH KORDON.

Bariloche, Río Negro, Argentina.

Congreso; Combined Meetings: "Gene Expression and RNA Processing" (ICGEB) and "Cell Biology, Signaling and Alternative Splicing" (EURASNET); 2007

ICGEB/EURASNET

Integrins belong to a superfamily of cell surface adhesion receptors that play a critical role in tumor progression as well as in a number of physiological processes. Particularly in mammary gland, the relevance of different expression patterns of b1 integrin for normal and tumor development has become evident. Based on numerous studies implicating 3’UTR sequences in the regulation of mRNA levels, we have examined gene products of b1 integrin in normal and neoplastic mammary glands by 3’RACE-PCR. Cloning and sequencing these reaction products we have found a new b1 integrin RNA species, 578bp shorter (S) than the previously reported (L). By sequence analysis we have determined that this different species arise from the use of alternative polyadenylation sites. Our analysis also revealed the presence of two AU-rich element (ARE) sequences, localized between those sites and, therefore, absent in the S mRNA. Based on these differences, using both semiquantitative RT-PCR and RNAse protection assays, we studied the levels of expression and ratio between the S and L b1 integrin mRNA species during mammary development and in mammary tumors. We found that although both S and L b1 integrin mRNA species have been detected in tumors and normal mammary glands, L levels are always higher. In addition, each stage of mammary gland development corresponds to a specific L/S ratio. We have subcloned the different 3’UTRs coming form the L and S forms into a reporter vector downstream of a CMV driven luciferase gene. In addition, we introduced a point mutation in the first construct that abolishes the first PolyA signal and only produces the L form. Working with HC11 normal epithelial mammary cells and mammary glands from different developmental stages we have found that estrogen levels influence PolyA site selection and mRNA levels. Combining all these tools, we are studying how different hormonal or developmental conditions regulate b1 integrin mRNA expression.