Evidences for miRNA regulation of BCL11A gene expression

In β-thalassemia reactivation of γ-globin genes and production of fetal hemoglobin (HbF) is clinically relevant. Interestingly, γ-globin gene expression is under a strong negative control performed by the transcription repressors BCL11A, KLF-1, MYB, Oct-1 and LYAR. Among these, BCL11A plays a pivotal role and it was recently shown by genome-wide association studies as the major repressor of HbF expression. The objective of this study was to determine whether microRNAs could be proposed as BCL11A regulators. This field of research is of top interest, since the objective of several approaches is the pharmacologic inhibition of the expression of γ-globin gene repressors, leading to γ-globin gene activation. MicroRNAs (miRNAs, miRs) are a category of conserved, short RNAs that target specific mRNA sequences, causing a post-transcriptional negative control of gene expression. The results obtained indicate that the coding sequence of BCL11A mRNA contains a putative miR-210 binding site, located at the level of a coding BCL11A mRNA sequence exhibiting partial single stranded secondary structure interactions. The extent of complementarity between this BCL11A sequence and mature miR-210 is 72.7%. The ability of miR-210 to interact with the miR-210 BCL11A mRNA binding site has been validated by SPR-based analysis with the BiacoreTM X100 biosensor. The miR-210 putative BCL11A mRNA binding sites are conserved through molecular evolution. In order to obtain information on the biological effects of miR-210 on BCL11A-regulated genes, a K562 clone expressing high BCL11A-XL levels was employed. Transfection of this clone with pre-miR-210 leads to a sharp concentration dependent decrease of BCL11A transcripts associated with increased γ-globin mRNA content. Other miRNAs putatively involved in BCL11A regulation (miR-26a, miR-30b and miR-148a) were identified to functionally interact with the 3’UTR BCL11A mRNA. Together with the data available in the literature, our findings suggest that regulation of BCL11A gene expression might be associated with microRNAs targeting BCL11A mRNA.