GC-elements controlling HRAS transcription form i-motif structures unfolded by heterogeneous ribonucleoprotein particle A1.

ABSTRACT: HRAS is regulated by two neighbouring quadruplex-forming GC-elements (hras-1 and hras-2), located upstream of the major transcription start sites (doi: 10.1093/nar/gku 5784). In this study we demonstrate that the C-rich strands of hras-1 and hras-2 fold into i-motif conformations (iMs) characterized under crowding conditions (PEG-300, 40% w/v) by semi-transitions at pH 6.3 and 6.7, respectively. Nondenaturing PAGE shows that the HRAS C-rich sequences migrate at both pH 5 and 7 as folded intramolecular structures. Chromatin immunoprecipitation shows that hnRNP A1 is associated under in vivo conditions to the GC-elements, while EMSA proves that hnRNP A1 binds tightly to the iMs. FRET and CD show that hnRNP A1 unfolds the iM structures upon binding. Furthermore, when hnRNP A1 is knocked out i

SUBMITTER: Miglietta G 

PROVIDER: S-EPMC4682182 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature