Characterization of the human MANB gene encoding lysosomal alpha-D-mannosidase

Genomic clones of human MANB gene encoding the lysosomal enzyme, alpha-mannosidase, have been isolated, sequenced and analyzed. The human MANB gene spans approximately 22 kb and consists of 24 exons. The 5' flanking region of the gene shows a high G+C content and has two Sp1 and three AP-2 sites. Promoter analysis using deletion constructs of the 5' flanking region fused to the bacterial CAT gene showed that 150 bp of 5' sequence could drive the expression of MANB in COS 7 cells. Determination of the sequence of the 5' end of the alpha-mannosidase mRNA by 5' RACE protocol showed that transcription is initiated from a cluster of sites centered -28 and -20 bp from the first in-frame ATG. These data demonstrate that, like other lysosomal enzyme genes such as those for beta-glucuronidase or beta-hexosaminidase, the human MANB gene is controlled by a short 5' flanking sequence located near the initiation codon.