Date of Award
1994
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
Catalases provide cellular protection against the effects of oxygen free radicals. In mice, catalase is coded for by a single gene, Cas-1, located on Chromosome 2, 48 cM from the centromere. A number of genetic strains with variable tissue-specific expression patterns permit the evaluation of molecular mechanisms for the regulation of this housekeeping enzyme.;Transcriptional and post-transcriptional mechanisms of catalase regulation were investigated. The first complete cDNA sequence of Cas-1 is presented and includes 1584 nucleotides encoding 528 amino acids. In addition, 659 bp of 5{dollar}\sp\prime{dollar} genomic upstream region of Cas-1 were sequenced revealing a "CG island", two putative CCAAT boxes, and a GC box. This promoter was examined for patterns of methylation which suggest that the tissue-specific expression of catalase is transcriptionally regulated.;Cas-1 expression was evaluated in mouse tissues of genetic strains and genotypes using enzyme activity assays, polypeptide (western blot) and mRNA analyses. The tissue-specific expression of catalase activity is reflected in the levels of mRNA and suggests transcriptional regulation. The variability in enzyme activity among strains/genotypes is not correlated with mRNA levels, rather it correlates with the level of polypeptide (western blot) suggesting post-transcriptional control. Post-transcriptional regulation is also evident during fetal development and differentiation including birth. The 3{dollar}\sp\prime{dollar} untranslated region (3{dollar}\sp\prime{dollar} UTR) of Cas-1 mRNA reveals several unusual near repeats ((CA){dollar}\sb{lcub}31{rcub},{dollar} (U){dollar}\sb{lcub}15{rcub}{dollar} and (UGUGC){dollar}\sb7\rbrack.{dollar} The mRNA gel shift assay was used to identify proteins which specifically complexed with (CA){dollar}\sb{lcub}31{rcub}{dollar} ({dollar}\sim{dollar}69 kDa) and (U){dollar}\sb{lcub}15{rcub}{dollar} ({dollar}\sim{dollar}38 and 47 kDa) sequences. In addition, the {dollar}\sim{dollar}69 kDa and the {dollar}\sim{dollar}38 kDa proteins are found associated with polysomes. The (U){dollar}\sb{lcub}15{rcub}{dollar}-protein complex may be involved in mRNA stability. Although the function of the (CA){dollar}\sb{lcub}31{rcub}{dollar}-protein complex was not established, it may aid in translational regulation by an undetermined mechanism. One possible model could involve "cross-talk" between the 5{dollar}\sp\prime{dollar} and 3{dollar}\sp\prime{dollar} UTRs of this mRNA via associated proteins. The sequence-specific proteins identified in these experiments may represent the trans-acting factors alluded to in a number of segregation studies on mouse catalases.
Recommended Citation
Reimer, Dorothy L., "The Molecular Genetics Of Mouse Catalase" (1994). Digitized Theses. 2434.
https://ir.lib.uwo.ca/digitizedtheses/2434