Identification of two novel 5' noncoding exons in human MNB/DYRK gene and alternatively spliced transcripts

Previously, the comparison of human MNB/DYRK cDNA sequences with publicly available genomic DNA sequence made a conclusion that MNB/DYRK gene consists of 11 exons spanning 100 kb. Here we found a novel human MNB/DYRK cDNA clone that has the 5' end different from any of those reported MNB/DYRK cDNAs. The 5' end of this cDNA resides in a CpG island associated with the NotI linking clone LL390 that is located more than 50 kb upstream of the exon that contains an initiation codon ATG. Northern blot analysis indicated that almost all the MNB/DYRK transcripts start from the newly identified 5'-noncoding exon. PCR amplification of cDNAs from various human tissues indicated that some mRNAs contain an additional noncoding exon of 76 bp next to the 5'-end exon and there are at least three types of MNB/DYRK mRNAs containing alternatively spliced 5' exons including two novel exons. We now conclude that human MNB/DYRK gene consists of 13 exons (not 11 exons) spanning about 150 kb (not 100 kb).