EVIDENCE FOR DEGRADATION OF MESSENGER-RNA ENCODING ALPHA-L-IDURONIDASE IN HURLER FIBROBLAST WITH PREMATURE TERMINATION ALLELES

Mutations in the gene encoding alpha-L-iduronidase (IDUA) are the caus e of Hurler syndrome. Fibroblasts from patients homozygous for nonsens e IDUA alleles have much reduced mRNA detectable by Northern analysis, as has been observed in many other instances of premature translation termination. Yet RT-PCR (reverse transcription followed by PCR amplif ication) showed a normal level of a segment covering exons 1 and 2 in Hurler cells homozygous for alleles bearing the nonsense mutations, Q7 0X or W402X. The 3' end of the segment was between exons 2 and 4. The results indicate that the nonsense RNA was degraded to fragment(s), in dependent of the position of the mutation (exon 2 or exon 9, respectiv ely). Treatment of the cells with cycloheximide resulted in some incre ase of intact mRNA, suggesting that translation is required for mRNA d egradation.