Progress in cell cycle research最新文献

Cyclin-dependent kinases are involved in diverse cellular processes that include cell cycle control, apoptosis, neuronal physiology, differentiation, and transcription. Intensive screening and drug design based on CDK/inhibitor co-crystal structures and on SAR studies have led to the identification and characterization of a large variety of chemical inhibitors of CDKs. Although they all act by competing with ATP for binding at the catalytic site of the kinase, their kinase selectivity varies greatly and remains to be studied in most cases. The requirement for CDKs in many physiological processes justifies their evaluation as potential therapeutic targets against a much larger scope of diseases than initially anticipated.

Malignant cells result from the accumulation of genetic alterations that impinge into the components of signal transduction pathways controlling cell growth, differentiation and apoptosis. One of the critical pathways is related to the regulation of the phospholipid homeostasis. The identification of the molecular components involved in normal cell growth regulation altered upon transformation is required for the development of chemotherapeutic interventions against transformed cells. Discovery of new chemotherapeutic agents is one of the most promising ways to improve our success against cancer, and rational drug design is a key factor to achieve this goal. Evidence supporting choline kinase and phospholipase D as such novel targets is provided.

The tumour suppressor activity of p53 plays a major role in limiting abnormal proliferation, and inactivation of the p53 response is becoming increasingly accepted as a hallmark of cancer. In contrast, both p63 and p73, which are close relatives of p53, are rarely mutated in tumour cells. At a theoretical level, therapeutic approaches that reinstate p53 activity, or augment p63 and p73, provide plausible and potentially efficacious routes towards new cancer treatments. Equally important is the clinical need to increase the efficacy of conventional anti-cancer drugs. Incapacitating the p53 response to limit the side effects in healthy cells may be one approach towards increasing the therapeutic window of many current anti-cancer drugs. Nevertheless, while cancer drug discovery focussed on p53 is an exciting and realistic possibility, translating this concept into a clinical setting is likely to be challenging.

Polyamines (putrescine, spermidine, and spermine) are ubiquitous cellular components that have multiple functions, including actions affecting the cell cycle. Polyamine biosynthesis and content is altered during the course of cell cycling via changes in two key biosynthetic enzymes, ornithine decarboxylase and S-adenosyl-methionine decarboxylase. Decreases in polyamine content and/or alterations in the relative amounts of polyamines can be achieved by treatment with inhibitors of these enzymes or by application of polyamine analogues, which subvert mechanisms for polyamine homeostasis and may interfere directly with polyamine-dependent processes. Such changes cause G1 and G2-M cell cycle blocks that can be brought about via induction of p21WAF1/CIP1.

It has been well known that cell-anchorage and the cell cytoskeleton are deeply involved in the regulation of cell proliferation and cell cycle. However, the precise molecular mechanism involved in cell-anchorage and the cell cytoskeleton have remained be to elucidated. The recent great volume of information regarding cell cycle regulators such as cyclin, cyclin-dependent kinases (CDKs) and CDK inhibitors (CKI) has facilitated the understanding of the cell cycle in mammalian cells. In this review, we will focus on these cell cycle regulators to discuss the regulation of cell proliferation controlled by cell-anchorage and the cytoskeleton, and especially the roles of Rho family GTPases.

Hamster rcc1 mutant, tsBN2, prematurely enter mitosis during S phase. RCC1 is a guanine nucleotide exchanging factor for a small G protein Ran and localised on the chromatin, whereas RanGTPase activating protein is in the cytoplasm. Consistently, Ran shuttles between the nucleus and the cytoplasm, carrying out nucleus-cytosol exchange of macromolecules, which regulates the cell cycle. The finding that loss of RCC1 which disturbs nuclear protein export due to loss of RanGTP, abrogates the check point control suggests that RCC1 senses the status of the chromatin, such as replication, and couples it to the cell cycle progression through Ran.

The ordered execution of the two main events of cellular reproduction, duplication of the genome and cell division, characterize progression through the cell cycle. Cultured cells can be switched between cycling and non-cycling states by alteration of extracellular conditions and the notion that a critical cellular control mechanism presides on this decision, whose temporal location is known as the restriction point, has become the focus for the study of how extracellular mitogenic signalling impinges upon the cell cycle to influence proliferation. This review attempts to cover the disparate pathways of Ras-mediated mitogenic signal transduction that impact upon restriction point control.

The critical steps of the cell cycle are generally controlled through the transcriptional regulation of specific subsets of genes. Transcriptional regulation has been recently linked to acetylation or deacetylation of core histone tails: acetylated histone tails are generally associated with active chromatin, whereas deacetylated histone tails are associated with silent parts of the genome. A number of transcriptional co-regulators are histone acetyl-transferases or histone deacetylases. Here, we discuss some of the critical cell cycle steps in which these enzymes are involved.

DBF4 and CDC7 were identified as budding yeast cell cycle mutants that arrest immediately before S phase. The Dbf4p and Cdc7p proteins interact to form a protein kinase, Cdc7p being the catalytic subunit and Dbf4p is a cyclin-like molecule that activates the kinase in late G1. Dbf4p also targets Cdc7p to origins of replication where likely substrates include the Mcm proteins. Dbf4p and Cdc7p related proteins occur in the fission yeast and in metazoans. These also phosphorylate Mcm proteins and preliminary evidence indicates a similar function to Dbf4p/Cdc7p in budding yeast. The Dbf4p/Cdc7p activity will therefore very likely be conserved in all eukaryotes.

Protein phosphorylation by proline-directed protein kinases plays an essential role in triggering a programmed set of cell cycle events. We have recently isolated an essential and conserved mitotic regulator, Pin1. Pin1 is a phosphorylation-dependent prolyl isomerase that specifically isomerizes the phosphorylated serine/threonine-proline bond. Pin1 also binds and regulates the function of a conserved set of mitosis-specific phosphoproteins. These results suggest phosphorylation-dependent prolyl isomerization to be a novel cell cycle regulatory mechanism. This new post-translational regulation may allow the general increase in protein phosphorylation to be converted into the organised and programmed set of structural modifications that occur during mitosis. In addition, since inhibition of Pin1 induces mitotic arrest and apoptosis, Pin1 may be a potential new drug target.