Higher processing rates of Alu-containing sequences in kidney tumors and cell lines with overexpressed Alu-mRNAs.

Tumor cell growth and differentiation involve several molecular mechanisms that control gene expression and define specific genomic molecular profiles in cancer cells. Among these mechanisms, it has been shown that Alu-repetitive sequences are capable of regulating gene expression at transcriptional and posttranscriptional levels, and also of modulating cellular growth, differentiation and tumor suppression. Furthermore, repetitive sequences have also been implicated in alternative RNA splicing, although the specific mechanisms involved remain unknown. Nonetheless, exactly what the involvement of Alu-containing sequences in tumor cell growth and differentiation is or to what extent they might be related to tumorigenesis or to alternative splicing is not yet clear. In order to address some of these issues, we analyzed the level of expression of Alu-containing sequences in renal tumors and cell lines and their association with immunoprecipitated ribonucleoprotein splicing complexes in nuclear RNA fractions. Over-expression of Alu-containing sequences was detected in the poly(A)-RNA fractions of all analyzed tumors and cell lines. Furthermore, Alu-sequences were associated with tumor cell growth and differentiation and found overexpressed in purified small nuclear ribonucleoprotein fractions. Overall, our results suggest the involvement of Alu-sequences in the overexpression of Alu-containing-mRNAs in human tumors, and also higher processing rates of Alu-containing sequences at the spliceosome associated with tumor cell growth and differentiation.