YB-1 transcription in the postnatal brain is regulated by a bHLH transcription factor Math2 through an E-box sequence in the 5'-UTR of the gene

YB-1 controls gene expression at both the transcriptional and translational levels. In the brain, a high level of YB-1 is expressed from prior to the first week after birth. However, YB-1 expression substantially declines to the adult level thereafter. Here, we investigated the regulatory mechanism of YB-1 transcription in the postnatal brain. We found that an E-box sequence within the 5'-untranslated region (5'-UTR) of the gene was recognized by Math2 in the 5-day-old brain, whereas the DNA binding was reduced in the 4-week-old brain. In vitro transcription analysis and reporter gene assay revealed that Math2 was necessary for YB-1 transcription. Furthermore, the expression pattern of Math2 protein in the postnatal brain was correlated with that of YB-1 protein. Our results suggest that YB-1 transcription in the postnatal brain is regulated by Math2, which binds to an E-box in the 5'-UTR of the YB-1 gene.