Refinement of the spectra of exon usage by combined effects of extracellular stimulus and intracellular factors

Biochim Biophys Acta. 2014 Jul;1839(7):537-45. doi: 10.1016/j.bbagrm.2014.05.002. Epub 2014 May 17.

Abstract

Finely tuned differential expression of alternative splice variants contributes to important physiological processes such as the fine-tuning of electrical firing or hearing frequencies; yet the underlying molecular basis for the expression control is not clear. The inclusion levels of four depolarization-regulated alternative exons were measured by RT-PCR in GH3 pituitary cells under different conditions of stimulation and/or RNA interference of splicing factors. The usage of the exons was reduced by membrane depolarization to various extents and was differentially modulated by the knock-down of splicing factors hnRNP L, L-like, I (PTBP1) or K or their combinations. A spectrum of each exon's level was produced under six knock-down conditions and was significantly shifted by depolarization. When all these conditions were considered together, a more refined or expanded spectrum of exon usage was obtained for each of the four exons. As a proof of principle for the molecular basis of the fine-tuning of exon usage, we show in the cases of hnRNP L and LL that their differential effects through the same element or different combinations of RNA sequences by the same factor hnRNP L are critical. The results thus demonstrate that the combined effect of varying extracellular stimuli and intracellular factors/RNA sequences refines or expands the spectra of endogenous exon usage, likely contributing to the fine-tuning of cellular properties.

Keywords: Alternative splicing; Membrane depolarization; PTBP1; hnRNP K; hnRNP L/LL.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing / genetics*
  • Exons / genetics
  • HEK293 Cells
  • HeLa Cells
  • Heterogeneous-Nuclear Ribonucleoprotein L / genetics*
  • Humans
  • RNA Interference
  • RNA Splicing / genetics*

Substances

  • Heterogeneous-Nuclear Ribonucleoprotein L