I read this book the same weekend that the Packers took on the Rams, and the experience of the latter event, obviously, colored my judgment. Although I abhor anything that smacks of being a handbook (like, \"How to Earn a Merit Badge in Neurosurgery\") because too many volumes in biomedical science already evince a boyscout-like approach, I must confess that parts of this volume are fast, scholarly, and significant, with certain reservations. I like parts of this well-illustrated book because Dr. Sj6strand, without so stating, develops certain subjects on technique in relation to the acquisition of judgment and sophistication. And this is important! So, given that the author (like all of us) is somewhat deficient in some areas, and biased in others, the book is still valuable if the uninitiated reader swallows it in a general fashion, realizing full well that what will be required from the reader is a modulation to fit his vision, propreception, adaptation and response, and the kind of problem he is undertaking. A major deficiency of this book is revealed by comparison of its use of physics and of chemistry to provide understanding and background for the application of high resolution electron microscopy to problems in biology. Since the volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of The instrument and its ancillary tools are simply and well presented. The potential use of chemical or cytochemical information as it relates to biological fine structure , however, is quite deficient. I wonder when even sophisticated morphol-ogists will consider fixation a reaction and not a technique; only then will the fundamentals become self-evident and predictable and this sine qua flon will become less mystical. Staining reactions (the most inadequate chapter) ought to be something more than a technique to selectively enhance contrast of morphological elements; it ought to give the structural addresses of some of the chemical residents of cell components. Is it pertinent that auto-radiography gets singled out for more complete coverage than other significant aspects of cytochemistry by a high resolution microscopist, when it has a built-in minimal error of 1,000 A in standard practice? I don't mean to blind-side (in strict football terminology) Dr. Sj6strand's efforts for what is \"routinely used in our laboratory\"; what is done is usually well done. It's just that …

Methods in Enzymology.

/pdf/recent-advances-in-the-biochemistry-of-polyamines-in-382j7cp9ea.pdf

Recent advances in the biochemistry of polyamines in eukaryotes.

Formation of mRNA 3′ ends in eukaryotes requires the interaction of transacting factors with cis-acting signal elements on the RNA precursor by two distinct mechanisms, one for the cleavage of most replication-dependent histone transcripts and the other for cleavage and polyadenylation of the majority of eukaryotic mRNAs. Most of the basic factors have now been identified, as well as some of the key protein-protein and RNA-protein interactions. This processing can be regulated by changing the levels or activity of basic factors or by using activators and repressors, many of which are components of the splicing machinery. These regulatory mechanisms act during differentiation, progression through the cell cycle, or viral infections. Recent findings suggest that the association of cleavage/polyadenylation factors with the transcriptional complex via the carboxyl-terminal domain of the RNA polymerase II (Pol II) large subunit is the means by which the cell restricts polyadenylation to Pol II transcripts. The processing of 3′ ends is also important for transcription termination downstream of cleavage sites and for assembly of an export-competent mRNA. The progress of the last few years points to a remarkable coordination and cooperativity in the steps leading to the appearance of translatable mRNA in the cytoplasm.

Formation of mRNA 3′ Ends in Eukaryotes: Mechanism, Regulation, and Interrelationships with Other Steps in mRNA Synthesis

https://www.gene-quantification.de/schmittgen-2-2000.pdf

Quantitative Reverse Transcription–Polymerase Chain Reaction to Study mRNA Decay: Comparison of Endpoint and Real-Time Methods☆

Summary: Evolution of RNA viruses occurs through disequilibria of collections of closely related mutant spectra or mutant clouds termed viral quasispecies. Here we review the origin of the quasispecies concept and some biological implications of quasispecies dynamics. Two main aspects are addressed: (i) mutant clouds as reservoirs of phenotypic variants for virus adaptability and (ii) the internal interactions that are established within mutant spectra that render a virus ensemble the unit of selection. The understanding of viruses as quasispecies has led to new antiviral designs, such as lethal mutagenesis, whose aim is to drive viruses toward low fitness values with limited chances of fitness recovery. The impact of quasispecies for three salient human pathogens, human immunodeficiency virus and the hepatitis B and C viruses, is reviewed, with emphasis on antiviral treatment strategies. Finally, extensions of quasispecies to nonviral systems are briefly mentioned to emphasize the broad applicability of quasispecies theory.

Viral Quasispecies Evolution

An alternative molecular mechanism of action of 5-fluorouracil, a potent anticancer drug

A heparin-sensitive nuclear protein kinase. Purification, properties, and increased activity in rat hepatoma relative to liver.

In eukaryotic cells, ribosomal RNA (rRNA) gene is transcribed by RNA polymerase I (pol I) in the nucleolus as a large (40 S-47 S) precursor RNA (pre-rRNA) (for reviews, see refs. [1,2]). The mature rRNA species (28 S, 18 S and 5.8 S) are formed after a series of specific endonucleolytic cleavage reactions (for a review, see ref. [3]). The rRNA gene (rDNA) is highly reiterated and is arranged in a tandem array in clusters of headto-tail repeats. Each transcription unit is separated from the next unit by an intergenic spacer that ranges in size from 2 kb to over 30 kb. The transcriptionally active rRNA genes can be visualized in electron micrographic spreads of nucleolar chromatin as structures resembling Christmas trees where the rRNA gene, functional RNA pol I molecules and growing RNA chains can be observed as discrete entities [4]. Ribosomal RNA accounts for

Regulation of ribosomal gene transcription

IT has been established that many eukaryotic mRNAs contain poly(adenylic acid) tracts at their 3′-termini. The polyadenylation of mRNA occurs post-transcriptionally in the nucleus as a rapid, initial addition of 100–200 adenylate residues to the pre-mRNA (ref. 1). Subsequently, a slower chain extension (6–8 bases) of the poly(A) tail seems to occur both in the nucleus and in the cytoplasm2. The initial polyadenylation reaction can be specifically inhibited by the drug cordycepin (3′-deoxyadenosine) in cell culture, presumably by its conversion to the triphosphate analogue which acts as a competitive inhibitor of poly(A) polymerase. Cordycepin, however, has little effect on the slower poly(A) extension reaction3 or on the formation of mRNA precursor molecules4–6; but it can inhibit rRNA synthesis7. Contrary to the in vitro observations, cordycepin 5′-triphosphate (3′dATP) is not a specific inhibitor of poly(A) synthesis in vivo, relative to RNA synthesis8,9, and RNA polymerase I (which synthesises rRNA) is actually less sensitive to inhibition by 3′dATP than RNA polymerase II (ref. 10) (which is presumed to be involved in the synthesis of mRNA). Since nuclear poly(A) polymerase occurs in two functional states as ‘free’ and ‘chromatin-bound’ forms11, we reasoned that if the chromatin-associated poly(A) polymerase were involved in the initial polyadenylation of mRNA, it might be selectively inhibited by 3′dATP. The present studies, designed to test such an idea, demonstrate that, as in vivo, the initial polyadenylation reaction can be selectively inhibited in vitro by low levels of 3′dATP. These data also show that higher levels of 3′dATP can inhibit RNA synthesis, ‘chromatin-bound’ RNA polymerase I activity being significantly more sensitive than the ‘bound’ RNA polymerase II activity.

Specific inhibition of chromatin-associated poly(A) synthesis in vitro by cordycepin 5'-triphosphate.

Regulation of gene expression in response to steroids, thyroid hormone, and retinoids is mediated by an impressive array of intracellular receptors. Sequence analysis showed that the hormone receptors comprise a large superfamily of ligand-responsive transcription factors. Upon binding to hormones, the receptors interact with specific hormone response elements located in the promoters of numerous genes. Promoter-bound receptors communicate with distinct receptors and/or additional members of the transcriptional machinery, frequently evoking protein-protein interactions. Ultimately, this results in the induction of complex gene systems that control hormone-induced processes such as differentiation, cell growth, and homeostasis. In addition to the genes transcribed by RNA polymerase II, the lipophilic hormones, particularly glucocorticoids, can also modulate RNA polymerase I-directed transcription of the ribosomal gene. For both transcription systems, activation and repression of genes in response to hormon...

Samson T. Jacob

Papers

An alternative molecular mechanism of action of 5-fluorouracil, a potent anticancer drug

A heparin-sensitive nuclear protein kinase. Purification, properties, and increased activity in rat hepatoma relative to liver.

Regulation of ribosomal gene transcription

Specific inhibition of chromatin-associated poly(A) synthesis in vitro by cordycepin 5'-triphosphate.

Control of gene expression by lipophilic hormones.