Functional Cis-acting Elements Research Articles

Cap-independent translation of poliovirus mRNA is conferred by sequence elements within the 5' noncoding region.

Poliovirus polysomal RNA is naturally uncapped, and as such, its translation must bypass any 5' cap-dependent ribosome recognition event. To elucidate the manner by which poliovirus mRNA is translated, we have determined the translational efficiencies of a series of deletion mutants within the 5' noncoding region of the mRNA. We found striking differences in translatability among the altered mRNAs when assayed in mock-infected and poliovirus-infected HeLa cell extracts. The results identify a functional cis-acting element within the 5' noncoding region of the poliovirus mRNA which enables it to translate in a cap-independent fashion. The major determinant of this element maps between nucleotides 320 and 631 of the 5' end of the poliovirus mRNA. We also show that this region (320 to 631), when fused to a heterologous mRNA, can function in cis to render the mRNA cap independent in translation.

DNA sequences required for expression of a Dictyostelium actin gene.

A 2.8-kb fragment of 5' non-coding DNA from the Dictyostelium actin 15 gene has previously been shown to contain all of the cis-acting DNA sequence elements required for normal developmentally-regulated transcription of actin gene fusion RNAs when reintroduced into the genome by DNA-mediated transformation. Deletion analysis of this promoter fragment indicates that all of the necessary information is contained within a 270-bp fragment of actin 15 5' non-coding DNA. This fragment contains four short G/C-rich repeated sequences that are also found in other co-regulated Dictyostelium actin genes. A 12-bp consensus sequence, AAAAATGGGG/ATT, is present in the regions essential for expression of two different Dictyostelium actin genes, actin 6 and actin 15, but is absent from an actin gene showing a different temporal pattern of developmental regulation. Deletion analysis and DNase I footprinting implicate this sequence as a functional cis-acting element required for transcription of the actin 15 gene.