The β‐globin C→G mutation at 6 bp 3′ to the termination codon causes β‐thalassaemia by decreasing the mRNA level

Abstract

Summary. We have studied the expression of the silent b-thalassaemia term+6 (C fi G) mutation, at nucleotide 6 after the stop codon within the human b-globin 3¢ untranslated regions (3¢UTR), by stable transfection in murine erythroleukaemia (MEL) cells. Steady state mRNA levels from transfected MEL cells containing the term+6 mutant allele were reduced by 52-60%, compared with those obtained from the normal b-globin gene, in both total and cytoplasmic RNA fractions, showing that the mutation itself is responsible for the similar data obtained from patients. Upon analysis of nuclear RNA, the term+6 mutation was found to also lower the ratio of cleaved/uncleaved transcripts by 22-30%, thus revealing that it interferes with correct 3¢-end formation of b-globin mRNA. The term+6 mutation lies within a polypyrimidine track, similar to that in the b-intervening sequence II (b-IVSII), which is known to be an important contributor to the promotion of premRNA 3¢-end formation. We propose that the two polypyrimidine tracks flanking the translated region of exon III of the human b-globin gene may co-operate during b-globin mRNA biogenesis.

Searching for potential microRNA-binding site mutations amongst known disease-associated 3′ UTR variants

“…This notwithstanding, it still remains possible that the variant G allele constitutes a miRNA target mutation. However, in this case, any ensuing functional consequences would have been concealed by a concomitant effect on mRNA stability, an effect already demonstrated by in vitro functional analysis (Sgourou et al 2002).…”

A 13-bp Deletion in the 3′ Untranslated Region of the β-Globin Gene Causes β-Thalassemia Major in Compound Heterozygosity with IVSII-1 Mutation

“…The 3 untranslated regions (3 UTR) have critical roles in pre-mRNA processing through the polyadenylation signal. The sequences downstream and upstream of this signal have been shown to be responsible for proper processing [1,2] . Therefore, some 3 UTR mutations are involved in the reduction of ␤ -globin chain production [1,3] .…”

“…The sequences downstream and upstream of this signal have been shown to be responsible for proper processing [1,2] . Therefore, some 3 UTR mutations are involved in the reduction of ␤ -globin chain production [1,3] . In this study, we describe hematological and molecular characteristics of a 13 -bp deletion in the 3 UTR of an Iranian family detected during prenatal diagnosis.…”

Control of human -globin mRNA stability and its impact on beta-thalassemia phenotype

“…Consistent with these data is the evidence that the naturally occurring C→G mutation 6 nt downstream of the normal termination codon fails to destabilize the corresponding bglobin mRNA. 38 Actually, the available data suggest that the α-and b-globin mRNA stability elements are structurally and functionally distinct. 3,36 An mRNP complex mediating the high stability of normal human b-globin mRNAs With the aim of characterizing trans-acting factors involved in the mechanism underlying the high stability of the human b-globin mRNA, Yu and Russell 39 described an mRNP complex that assembles on the 3'UTR of the bglobin mRNA and exhibits some of the properties of the α-complex.…”