Three Unique 5′ Untranslated Regions Are Spliced to Common Coding Exons of High‐ and Low‐Molecular‐Weight Microtubule‐Associated Protein‐2

Abstract: Three unique 5′ untranslated regions (UTRs) have been characterized for human microtubule‐associated protein‐2 (MAP‐2) transcripts. All three UTRs shared a common 171‐bp sequence adjacent to the MAP‐2 coding region and then diverged upstream. The size of the unique upstream sequence was 281, 146, or 104 bp. PCR of genomic DNA demonstrated that the 5′ UTRs span multiple exons. The unique region of the UTRs recognizes a 9.5‐ and a 6‐kb MAP‐2 transcript in poly(A)⁺ mRNA isolated from human MSN cells, and PCR analysis demonstrated that each unique UTR is contained in multiple high‐ and low‐molecular‐weight MAP‐2 transcripts. Reverse transcription‐PCR (RT‐PCR) performed on MSN mRNA isolated from polysomes demonstrated that all three of the UTRs contained within multiple MAP‐2 transcripts were associated with polysomes and hence translated. RT‐PCR from human fetal spinal cord and adult brain mRNA demonstrated that all of the UTRs are expressed at these developmental time points.