A SECRETED DNA-BINDING PROTEIN THAT IS TRANSLATED THROUGH AN INTERNALRIBOSOME ENTRY SITE (IRES) AND DISTRIBUTED IN A DISCRETE PATTERN IN THE CENTRAL-NERVOUS-SYSTEM

Internal initiation of translation, a mechanism infrequently used by c ellular messages, avoids the requirement of a methyl cap structure for translation of messenger RNAs. The mRNA transcript encoding the DNA-b inding protein MYT2 represents one of the exceptional cellular message s that contains an internal ribosome entry site (IRES), The RNA pseudo knot structure located in the 5 ' untranslated region of MYT2 function s to promote translation in vivo. MYT2 was cloned by its specific bind ing to a TTCCA motif in the promoter region of a glial-specific gene, myelin proteolipid protein. MYT2 also recognizes single-stranded nucle ic acids. In the central nervous system, MYT2 protein is found in olig odendrocyte progenitor cells, subsets of neurons, and cells of the cho roid plexus together with ciliated ependymal cells. MYT2 protein can a lso be secreted from cells, an atypical event for a DNA-binding protei n. The presence of an internal ribosome entry site in MYT2, together w ith the unusual localization of MYT2, suggests that this nucleic acid- binding protein may be in the class of proteins involved in cellular g rowth control and survival in the nervous system.