Folate receptors (PR) are inversely regulated by extracellular folate concentrations. Since FR regulation is primarily mediated at the translational level in cervical carcinoma (HeLa-IU,) cells which express FR-a mRNA, the potential for interaction of ciselements (FR-0 mRNA) and Irons-factors from these cells was determined. Using gelshift assays, two signals were identified which specifically derived from interaction of the 5′-untranslated region of FR-t.mRNA with cytosolic extracts from HeLa-IU, cells. RNase T l mapping revealed that both signals were from protein(s) interacting with two partially overlapping RNA sequences between nucleotides -133 to -116 and -158 to -116, upstream of the translation start site. Selective RNase H cleavage following hybridization with 18-mer antisense DNA complementary to the 18-base RNA fragment abolished both signals indicating that the 18-base RNA sequence is the cis-element. The interaction of this c/s-element and cytosolic protein was competed by poly(C), but not by poly(U), homopolymers. Cross-linking studies using ultra-violet light and Northwestern blot analysis confirmed that the 18-base cis-element specifically bound -46-kDa proteins. From the standpoint of assigning a function to the interaction of this cu-element and Svw-factor within the context of FR and folate metabolism, preliminary studies revealed that although these 46-kDa proteins were unaltered by extracellular folate concentrations, they were widely distributed in cells expressing little to no FR. Thus, the functional significance of this RNA-protein interaction warrants further study.
|Original language||English (US)|
|Journal||Journal of Investigative Medicine|
|State||Published - Jan 1 1996|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)