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Translation of cellular and early vaccinia RNA in nuclease-treated lysates, derived from uninfected and vaccinia-virus-infected cells al the early stage, has been investigated. When using limiting amounts of RNA no discrimination of translation was observed in the infected cells lysates; This conclusion was confirmed by sensitive RNA competition experiments for translation in vitro and also when using two different fractionated systems for protein synthesis in vitro. This absence of detectable discrimination in vitro was established both by comparing incorporation of [35S]methionine into proteins and by analysis of the products thus synthesized by sodium dodecylsulfate gel electrophoresis. However, a modification of the translational machinery from vaccinia-virus-infected cells did occur since only the ribosomal salt wash derived from infected cells was able to reverse the inhibition of protein synthesis in vitro resulting from excess RNA (control or early). This property of vaccinia-virus-infected cell lysates may result from the synthesis of an early protein involved in translation or from a better recovery of translational factors from the infected cells., as suggested in the accompanying paper. [ABSTRACT FROM AUTHOR]

Upon addition of lens polyribosomes to a reticulocyte-cell-free system, α, βL, and γ crystallin are synthesized, while βH crystallin is not formed. This phenomenon is comparable to the biosynthetic events in the lens-cell-free system and in tissue culture. It is shown that βH crystallin formation depends upon the presence of a polypeptide βB1b which arises by posttranslational modification. The putative precursor for βB1b is a polypeptide βB1a of which the messenger with a sedimentation coefficient of 12.5 S has been isolated. [ABSTRACT FROM AUTHOR]

The labeling kinetics of rRNA in exponentially growing Tetrahymena pyriformis were analyzed quantitatively in order to determine pool-sizes and turnover rates of nuclear 17 and 25 S rRNA. The mathematical analysis of the system indicates that, during the steady state of growth, there is an inverse proportionality between pool-size and turnover rate of nuclear rRNA. Thus, from the labeling kinetics of rRNA and the growth rate constant (4.6 × 10-3 min-1), the pool-size of macronuclear 17 S rRNA was estimated at 0.5% of that of cytoplasmic 17 S rRNA corresponding to a turnover rate constant of 0.92 min-1 The analogues figures for 25 S rRNA were estimated at 1.6% and 0.29 min-1. Since the RNA content of macronuclei is about 2% of the cellular RNA content, it is concluded that during growth, most nuclear RNA is found in precursors of ribosomes and that macronuclei contain few, if any, finished ribosomes. Apart from its nsc on rRNA, the method described here may be generally useful in determining pool-sizes and turnover rates of other precursors, such as free ribosomal proteins. [ABSTRACT FROM AUTHOR]