Maturation-promoting factor induces nuclear envelope breakdown in cycloheximide-arrested embryos of Xenopus laevis

We have studied the effect of maturation-promoting factor (MPF) on embryonic nuclei during the early cleavage stage of Xenopus laevis development. When protein synthesis is inhibited by cycloheximide during this stage, the embryonic cell cycle arrests in an artificially produced G2 phase-like state, after completion of one additional round of DNA synthesis. Approximately 100 nuclei can be arrested in a common cytoplasm if cytokinesis is first inhibited by cytochalasin B. Within 5 min after injection of MPF into such embryos, the nuclear envelope surrounding each nucleus disperses, as determined histologically or by immunofluorescent staining of the nuclear lamina with antilamin antiserum. The breakdown of the nuclear envelope occurs at levels of MPF comparable to or slightly lower than those required for oocyte maturation. Amplification of MPF activity, however, does not occur in the arrested egg as it does in the oocyte. These results suggest that MPF can act to advance interphase nuclei into the first events of mitosis and show that the nuclear lamina responds rapidly to MPF.     

Maturation-promoting factor and p34cdc2 kinase during oocyte maturation of the Japanese quail

Maturation-promoting factor and a homolog of fission yeast cdc2+ gene product (p34cdc2) were investigated during the final 24 hr of maturation of quail oocytes. Kinase activity of p34cdc2 in the oocyte germinal disk (GD) increased 15 times at maturation. Two bands, at 32 and 34 kDa, were detected in immature oocytes by immunoblotting of SDS-PAGE with anti-p34cdc2 monoclonal antibody. A new band, which is close to the 32-kDa band but with a slightly faster mobility, appeared during maturation. No p34cdc2 could be detected outside the GD. Microinjection of GD extract from mature oocytes caused maturation of Xenopus oocytes.     

VDAC, The early days

VDAC is now universally accepted as the channel in the mitochondrial outer membrane responsible for metabolite flux in and out of mitochondria. Its discovery occurred over two independent lines of investigation in the 1970s and 80s. This retrospective article describes the history of VDAC's discovery and how these lines merged in a collaboration by the authors. The article was written to give the reader a sense of the role played by laboratory environment, personalities, and serendipity in the discovery of the molecular basis for the unusual permeability properties of the mitochondrial outer membrane. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.     

VDAC,The early days

VDAC is now universally accepted as the channel in the mitochondrial outer membrane responsible for metabolite flux in and out of mitochondria. Its discovery occurred over two independent lines of investigation in the 1970s and 80s. This retrospective article describes the history of VDAC's discovery and how these lines merged in a collaboration by the authors. The article was written to give the reader a sense of the role played by laboratory environment, personalities, and serendipity in the discovery of the molecular basis for the unusual permeability properties of the mitochondrial outer membrane. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.     

Maturation-promoting factor governs mitogen-activated protein kinase activation and interphase suppression during meiosis of rat oocytes

Meiosis is a particular example of a cell cycle, characterized by two successive divisions without an intervening interphase. Resumption of meiosis in oocytes is associated with activation of maturation-promoting factor (MPF) and mitogen-activated protein kinase (MAPK). The activity of MPF declines during the transition between the two meiotic divisions, whereas the activity of MAPK is sustained. Attempts to disclose the interplay between these key regulators of meiosis in both amphibian and mammalian oocytes generated contradictory results. Furthermore, the enzyme that governs the suppression of interphase in mammals is still unidentified. To our knowledge, we provide herein the first demonstration in a mammalian system that inhibition of MPF at reinitiation of meiosis abrogated Mos expression and MAPK activation. We also show that oocytes, in which reactivation of MPF at completion of the first telophase was prevented, exhibited an interphase nucleus with decondensed chromosomes. Inhibition of MAPK did not interfere with the progression to the second meiotic metaphase but, rather, resulted in parthenogenic activation. We conclude that in rat oocytes, MPF regulates MAPK activation and its timely reactivation prevents the oocytes from entering interphase.     

The early days of DNA sequences

Fred Sanger was awarded the rare distinction of two Nobel Prizes for Chemistry, in 1958 and 1980. The first was for his work on the structure of proteins, particularly that of insulin, the latter for his contribution concerning the determination of nucleic acid sequences, the foundation work that ultimately led to The Human Genome Project.     

The early days of bioinformatics publishing

A brief history of the early days of publishing in the bioinformatics field is presented.     

My early days in photobiology with Philip Hanawalt

Phil and I started our careers on somewhat similar scientific paths. I had an undergraduate degree in physics from Swarthmore College and a Ph.D. degree in physics from Yale for research in the field for ultraviolet spectroscopy. Phil received an undergraduate degree in Physics from Oberlin College, joined the Yale Physics Department in 1954, and transferred to the new Biophysics Department in 1955. We began our interactions then by virtue of the fact that Phil had to take a Laboratory Course in Experimental Physics, one part of which was spectroscopy in which I was the instructor. One of my principal interests was in the effects of different wavelengths of ultraviolet (UV) radiation on proteins, viruses and bacterial cells. So what was more natural than for Phil to dream up a Ph.D. research project to investigate the effects of different wavelengths of UV on macromolecular synthesis in Escherichia coli. I became his mentor with expertise in UV, whereas he did most of the microbiological/biochemical work. Thus began a collaboration and a communicating friendship, the latter going on for 50 years. That communication was essential in elucidating some of the important steps in nucleotide excision repair-a field in which Phil is a pre-eminent scholar and investigator.     

成熟促进因子及其对卵母细胞成熟调控机制研究的新进展

卵母细胞成熟调控机制一直是发育生物学和生殖生物学领域的热点问题。以现代分子生物学理论为基础,科学家们对卵母细胞成熟分裂的分子生物学调控机理进行了大量研究。发现了细胞周期中许多关键的调控因子：cdc基因、周期蛋白依赖性激酶(CDKs)及细胞周期蛋白(cyclin)。本文对卵母细胞成熟调控的核心调控物质——成熟促进因子(maturation—promoting factor,MPF)的分子结构、周期变化及其在卵母细胞成熟过程中与丝裂原激活蛋白激酶(mitogen—activated protein kinase,MAPK)相互作用关系的最新进展进行了综述。     

Richard Pattle and the early days of comparative respiratory biology

After a distinguished academic career Richard Pattle was well qualified as a Physicist and Physical Chemist. Following a brief spell in the army (REME) he was appointed as a biophysicist in the Chemical Defence Experimental Laboratory at Porton Down. Such centres here and in USA initiated work which led to important discoveries relating to lung surfactants. His 1955 paper led to an expansion in studies of surfactant and the lung lining and appreciation of its importance in Respiratory Distress Syndrome of the newborn. This period (late 1950s and 1960s) was also when comparative studies in respiration were beginning to expand. Because of the relevance of his work to RDS it was inevitable that Pattle became closely associated with Human Physiologists. But he was also interested in other mammals and later the lungs of primates and lower vertebrates and this was extended to fish and the transition from water to air breathing. It was a time notable for the getting-together of medically-trained and zoologically-based scientists. I was always fascinated by the simplicity of his bubble technique and encouraged him to summarise it and his findings at Bhagalpur in 1974 when he introduced the term 'surpellic'. He also made important studies on bird lung surfactants.