Effect of Modulation of hnRNP L Levels on the Decay of bcl-2 mRNA in MCF-7 Cells

Abstract

It has been shown that CA repeats in the 3'-untranslated region (UTR) of bcl-2 mRNA contribute the constitutive decay of bcl-2 mRNA and that hnRNP L (heterogenous nuclear ribonucleoprotein L) interacts with CA repeats in the 3'-UTR of bcl-2 mRNA, both in vitro and in vivo. The aim of this study was to determine whether the alteration of hnRNP L affects the stability of bcl-2 mRNA in vivo. Human breast carcinoma MCF-7 cells were transfected with hnRNP L-specific shRNA or hnRNP L-expressing vector to decrease or increase hnRNP L levels, respectively, followed by an actinomycin D chase. An RT-PCR analysis showed that the rate of degradation of endogenous bcl-2 mRNA was not affected by the decrease or increase in the hnRNP L levels. Furthermore, during apoptosis or autophagy, in which bcl-2 expression has been reported to decrease, no difference in the degradation of bcl-2 mRNA was observed between control and hnRNP L-knock down MCF-7 Cells. On the other hand, the levels of AUF-1 and nucleolin, transacting factors for ARE in the 3'UTR of bcl-2 mRNA, were not significantly affected by the decrease in hnRNP L, suggesting that a disturbance in the quantitative balance between these transacting factors is not likely to interfere with the effect of hnRNP L. Collectively, the findings indicate that the decay of bcl-2 mRNA does not appear to be directly controlled by hnRNP L in vivo.

DSCAM-AS1-Driven Proliferation of Breast Cancer Cells Involves Regulation of Alternative Exon Splicing and 3′-End Usage

“…The stability of the antiapoptotic gene BCL2 was previously reported to be regulated by hnRNPL, which prevents the trigger of the NMD by directly interacting with the longer 3′UTR of the gene [ 16 ]. However, the study from Lim and colleagues suggested that the 3′UTR splicing of BCL2 is independent of hnRNPL in MCF-7, proposing the presence of an unknown factor interacting with the hnRNPL in the regulation of this splicing event [ 50 ]. In our data, the shortening of the BCL2 isoform, as well as the gene downregulation, is coherent with the impairment of hnRNPL-mediated stability, which could be directly mediated by the interaction with DSCAM-AS1 .…”

Retracted: Effects of RNA interference‐mediated silencing of toll‐like receptor 4 gene on proliferation and apoptosis of human breast cancer MCF‐7 and MDA‐MB‐231 cells: An in vitro study

“…Bcl-2, a gene from the Bcl family of genes that encodes specific protein, which regulates programmed cell death in pathological, and pathological conditions, is a representative anti-apoptotic protein; the levels of Bcl-2 affects cellular fates, death, or survival (Lim et al, 2010).…”

“…The continued existence of CDK4 has been associated with maintenance of tumor cell proliferation (Yu et al, 2006). P53 is a transcription factor that senses DNA damage, DNA repair, cell apoptosis, and cell cycle arrest; moreover, inactivating mutations of Bcl-2, a gene from the Bcl family of genes that encodes specific protein, which regulates programmed cell death in pathological, and pathological conditions, is a representative anti-apoptotic protein; the levels of Bcl-2 affects cellular fates, death, or survival (Lim et al, 2010).…”

hnRNP L‐dependent protection of normal mRNAs from NMD subverts quality control in B cell lymphoma

“…Approximately 50% of t(14:18) translocations associated with B cell lymphoma occur in the BCL2 major breakpoint region (MBR), fusing a portion of the IGH locus on chromosome 14 to the last exon of BCL2 on chromosome 18 and causing BCL2 transcriptional activation by the IGH l enhancer (Cleary et al, 1986;Seto, 2002;Deng et al, 2007). At the mRNA level, MBR translocations preserve the BCL2 ORF, TC, and proximal~2,500 nt of its 3 0 UTR (including protective hnRNP L binding sites), but the distal half of the BCL2 3 0 UTR is replaced by 4-6 IGH exons, depending on which IGH polyadenylation signal is used ( Fig 5B; Cleary et al, 1986;Lim et al, 2010). These exons are efficiently spliced and would be expected to lead to EJC deposition and NMD.…”