Methylation Status of SP1 Sites within miR-23a-27a-24-2 Promoter Region Influences Laryngeal Cancer Cell Proliferation and Apoptosis

Abstract

DNA methylation plays critical roles in regulation of microRNA expression and function. miR-23a-27a-24-2 cluster has various functions and aberrant expression of the cluster is a common event in many cancers. However, whether DNA methylation influences the cluster expression and function is not reported. Here we found a CG-rich region spanning two SP1 sites in the cluster promoter region. The SP1 sites in the cluster were demethylated and methylated in Hep2 cells and HEK293 cells, respectively. Meanwhile, the cluster was significantly upregulated and downregulated in Hep2 cells and HEK293 cells, respectively. The SP1 sites were remethylated and the cluster was significantly downregulated in Hep2 cells into which methyl donor, S-adenosyl-L-methionine, was introduced. Moreover, S-adenosyl-L-methionine significantly increased Hep2 cell viability and repressed Hep2 cell early apoptosis. We also found that construct with two SP1 sites had highest luciferase activity and SP1 specifically bound the gene cluster promoter in vitro. We conclude that demethylated SP1 sites in miR-23a-27a-24-2 cluster upregulate the cluster expression, leading to proliferation promotion and early apoptosis inhibition in laryngeal cancer cells.

Genetic Variation in Intergenic and Exonic miRNA Sequence and Risk of Multiple Sclerosis in the Isfahan Patients

“…In a study conducted in China, showed that mir-23a in Serum has a potential biomarker for recognition of type 2 diabete. [17][18][19][20][21][22] An exonic mir-155 with rs767649 (T/A) polymorphism in the upstream region of the pre-mir-155 gene is transcribed from the B-cell integration cluster (BIC). It has been suggested that mir155 modulate host antiviral immune response by elevating type I IFN signaling, and contribute in diverse biological processes such as immunity.…”

A miRNA signature suggestive of nodal metastases from laryngeal carcinoma

“…miR 24: its upregulation, similar to miR27a, leads to promotion of proliferation and early apoptosis inhibition in LSCC 18 ; according to Xu et al, miR24 expression is significantly lower in LSCC cell lines and it inhibits growth-related apoptosis and enhances radiosensitivity in LSCC 36 .…”

Radiation induced transcriptional and post-transcriptional regulation of the hsa-miR-23a ~ 27a ~ 24-2 cluster suppresses apoptosis by stabilizing XIAP

“…To determine whether reported methylation of the miR-23a~27a~24-2 cluster promoter [21] accounts for the transcriptional change after radiation, methylation was blocked 3 h prior to (Fig. 2B).…”

“…Evidence for a link between transcriptional repression and methylation of the cluster promoter comes from the study of Wang and Zhang et al [21]. These authors showed that demethylated SP1 sites in GC-rich regions of the cluster promoter result in over-expression of hsa-miR-23a~27a~24-2 in laryngeal cancer cells.…”

“…The microRNAs miR-23a, miR-27a and miR-24-2 are encoded by an intergenic cluster located on chromosome 19 with a promoter spanning from -603 to +36 relative to the transcription initiation site (+1) [20,21]. It is transcribed by polymerase II into a common primary (pri) transcript and is further processed into individual mature miRNAs ( Fig.…”