The ability to recognize that a genetic disease is caused by an abnormality in translational control must be based upon the definition of the mRNA structural features normally important in translation. Identification of such genetic defects may expand the understanding of pathogenesis in certain human genetic disorders such as the thalassemias and establish a scientific foundation for incorporating translational controls into the design of therapeutic approaches.
The specific aim of the proposed program is to study the genetic control of translation by defining the structural features of the two highly homologous human Alpha-globin mRNAs which result in their different translational efficiencies. The translational efficiencies of each of the two Alpha-globin mRNA species will be established in vivo and in vitro by combining accurate measurements of Alpha 1- and Alpha 2-globin mRNA levels with genetic approaches which allow quantitation of Alpha 1- and Alpha 2-globin protein synthesis. The following potential differences between the two Alpha-globin mRNA will be investigated and related to their relative translational efficiencies: a) the subcellular distrubution (sequestration in mRNP particles, association with polysomes), b) translation initiation efficiencies, and c) post-transcriptional structural modifications (5 feet capping, 3 feet polyadenylation). The translation of the two Alpha-globin mRNAs will be compared in erythroid and non-erythroid systems in vitro to detect erythroid-specific translation factors. Such factors will be characterized by reciprocal mixing experiments between the two systems. These factors will be localized to the ribosomal and/or post-ribosomal fractions, and their final isolation will be approached by RNA affinity chromatography. The 3 feet nontranslated region of the Alpha-globin mRNA will be altered by introducing deletions of primary sequences and interruptions of secondary structure to directly test the effects of this region upon translation and to specifically characterize regulatory sequences.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases (NIADDK)
Type
Research Project (R01)
Project #
5R01AM033975-03
Application #
3153035
Study Section
Physiological Chemistry Study Section (PC)
Project Start
1983-09-30
Project End
1987-08-31
Budget Start
1985-09-01
Budget End
1987-08-31
Support Year
3
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Shakin-Eshleman, S H; Liebhaber, S A (1988) Influence of duplexes 3' to the mRNA initiation codon on the efficiency of monosome formation. Biochemistry 27:3975-82
Liebhaber, S A; Cash, F E; Cornfield, D B (1988) Evidence for posttranslational control of Hb C synthesis in an individual with Hb C trait and alpha-thalassemia. Blood 71:502-4
Liebhaber, S A; Coleman, M B; Adams 3rd, J G et al. (1987) Molecular basis for nondeletion alpha-thalassemia in American blacks. Alpha 2(116GAG----UAG). J Clin Invest 80:154-9
Shakin, S H; Liebhaber, S A (1987) Opposite responses of rabbit and human globin mRNAs to translational inhibition by cap analogues. Biochemistry 26:7188-93
Moi, P; Cash, F E; Liebhaber, S A et al. (1987) An initiation codon mutation (AUG----GUG) of the human alpha 1-globin gene. Structural characterization and evidence for a mild thalassemic phenotype. J Clin Invest 80:1416-21
Shakin, S H; Liebhaber, S A (1986) Translational profiles of alpha 1-, alpha 2-, and beta-globin messenger ribonucleic acids in human reticulocytes. J Clin Invest 78:1125-9
Shakin, S H; Liebhaber, S A (1986) Destabilization of messenger RNA/complementary DNA duplexes by the elongating 80 S ribosome. J Biol Chem 261:16018-25
Liebhaber, S A; Cash, F E; Ballas, S K (1986) Human alpha-globin gene expression. The dominant role of the alpha 2-locus in mRNA and protein synthesis. J Biol Chem 261:15327-33
Liebhaber, S A; Cash, F E (1985) Locus assignment of alpha-globin structural mutations by hybrid-selected translation. J Clin Invest 75:64-70
Liebhaber, S A; Cash, F E; Main, D M (1985) Compensatory increase in alpha 1-globin gene expression in individuals heterozygous for the alpha-thalassemia-2 deletion. J Clin Invest 76:1057-64