COMPLETE SEQUENCE OF 3'-UNTRANSLATED REGION OF TAU FROM RAT CENTRAL-NERVOUS-SYSTEM - IMPLICATIONS FOR MESSENGER-RNA HETEROGENEITY

Tau is a family of microtubule associated proteins, heterogenous in mo lecular weights, which are expressed specifically in neurons. Tau is e ncoded by a single gene, while its transcript undergoes a complex and regulated alternative splicing, giving rise to several mRNA species th at migrate on Northern blots at approximately 6 and 2 kb. In this repo rt we characterize a full size transcript of tau mRNA from rat brain a nd demonstrate that it contains 5203 nucleotides (not including exon 2 and 3), which correlates well with the exact size of the transcript a s analyzed by Northern blot using RNA standard size markers. The full length of the 3'-untranslated region contains 3848 bp and includes two polyadenylation signals which may yield the two size transcripts in t he central nervous system. The first polyadenylation signal is located in the retained intron 13/14 and the second polyadenylation signal is 19 nucleotides before the poly(A) tail. Unspliced intron 13/14 was de tected in all RNA preparations tested, including RNA from different ag es and different regions of rat brain, RNA from dorsal root ganglia an d from undifferentiated and differentiated PC12 cells. In none of the above tissues and cells was a spliced transcript lacking intron 13/14 detected.