A complex between initiation factor IF‐2 and fMet‐tRNA can be formed under ionic conditions, which are optimal for initiation complex formation. The complex can be retained on cellulose nitrate ...filters after fixing with glutaraldehyde.
The IF‐2 · fMet‐tRNA complex formation is not influenced by GTP and GDP. Other nucleoside di or triphosphates also have no effect. Evidence is presented that this complex acts as an intermediate in polypeptide chain initiation. The IF‐2 · fMet‐tRNA complex formation is not influenced by initiation factors IF‐1 and IF‐3.
The binary complex can be bound to the 30‐S subunit in the absence of GTP, which indicates that there is no concomittant binding of the IF‐2 · fMet‐tRNA complex and the nucleotide moiety to the 30‐S subunit. The binding of the binary complex is stimulated by GTP. The influence of some inhibitors of initiation on the IF‐2 · fMet‐tRNA complex formation has been tested. Aurin tricarboxylic acid appeared to be a strong inhibitor, whereas the sulfhydryl reagents N‐ethylmaleimide and p‐chloromercuribenzoate had no effect.
In this paper the mode of action of IF‐1 in 40‐S initiation complex formation was studied with MS 2 RNA as messenger. Using initiation factors IF‐2 and IF‐3 labeled in vitro it appeared that IF‐1 did ...not influence the binding of these factors in the absence of fMet‐tRNA. However, in the presence of fMet‐tRNA it was found that the enhancement of the fMet‐tRNA binding by IF‐1 was accompanied with an equimolar increase in binding of IF‐2. Moreover, it appeared that also in absence of IF‐1, fMet‐tRNA binding is coupled with an equimolar enhancement of the IF‐2 binding, which suggests the existence of a preribosomal complex between IF‐2 and fMet‐tRNA. The apparent Km values for both the binding of fMet‐tRNA and IF‐2 to 30‐S subunits were determined and appeared to be equal, which makes a functioning of such a preribosomal complex in protein initiation very likely. The participation of GTP in this complex will be discussed. Functions of IF‐1 in dissociation and recycling of IF‐2, described by others, and the stimulation on the 30‐S subunit level might well be explained as pleiotropic effects of one basic action of IF‐1, i.e. a conformational change of 30‐S subunits.
Genome-wide measures of gene expression have been used to classify breast tumors into clinically relevant subtypes, as well as provide a better means of risk assessment on an individual basis for ...lymph node-negative (LNN) breast cancer patients. We have applied Affymetrix GeneChips of 22,000 transcripts to analyze total RNA of frozen tumor samples from 286 LNN breast cancer patients in order to identify a gene signature for identification of patients at high risk for distant recurrence.
New Tumor Biomarkers Brünner, Nils; Holten-Andersen, Mads; Sweep, Fred ...
Cancer Proteomics
Book Chapter
This chapter describes the key elements in tumor biomarker development toward clinical use. In particular, it focuses on the analytical aspects of assay development and how to implement new tumor ...biomarkers in the clinical setting.
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