Folate receptors (FR) are inversely regulated by the extracellular folate concentration at the translational level in cervical carcinoma cells. Accordingly, the potential for interaction of cis-elements in FR-α mRNA and trans-factors in these cells was determined. Gel-shift assays identified two signals that were specifically derived from the interaction of cytosolic proteins with the 5'-untranslated region of FR-α mRNA. RNase T1 mapping revealed that the RNA sequences interacting with these proteins were located between nucleotides -133 to -116 (18-bases) and -158 to -116 (43-bases), upstream of the translation start site. However, selective RNase H cleavage indicated that the 18-base RNA sequence was the cis-element. The RNA-protein interaction was competed by poly(C), but not by poly(U), homopolymers. UV cross-linking and Northwestern blot analysis confirmed that the trans- factors were 46-kDa proteins. An 18-base antisense oligodeoxynucleotide complementary to the cis-element specifically quenched the RNA-protein interaction and also completely inhibited translation of FR-α mRNA without changing its stability. Thus, the interaction of the 18-base cis-element and the 46-kDa trans-factors likely have an important role in translational regulation of FR. In addition, because the 46-kDa proteins were widely distributed in cells expressing little to no FR-α, these species probably have additional functions that are unrelated to translation of FR.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Biological Chemistry|
|State||Published - Oct 19 1996|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology