Genotoxic stress caused by carcinogens like Cigarette smoke activate both the MAPK pathway and the S phase checkpoint in Schizosaccharomyces pombe. But the cross talk between these two pathways has not been investigated in great detail in fission yeast. This study deals with the molecular mechanism of co-ordination between the two regulatory pathways. We show that both the pathways have a common effector molecule, namely Cdc25, the cell cycle regulatory phosphatase. We demonstrate that the MAPK Sty1 interacts with Cdc25 and prevents mitotic entry in S. pombe cells exposed to CSE. To our knowledge, this is the first demonstration of interaction between Sty1 and Cdc25 in S. pombe. The functional significance of this interaction lies in effecting Cdc25 turnover after CSE exposure in S. pombe. We show that Cdc25 turnover after CSE treatment is dependent on the presence of Rad3 activity and Sty1-Cdc25 interaction. Our study suggests that the Cigarette Smoke Extract (CSE) induced stress is counteracted by the simultaneous activation of a mitotic checkpoint in addition to the previously described S phase checkpoint. We also show that Sty1 activity is not essential for activation of the S phase checkpoint. ©2008 Landes Bioscience.

GEETANJALI SUNDARAM

Bio-Chemistry

S PALCHAUDHURI

S DIXIT

D CHATTOPADHYAY

Fulltext

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Cell Cycle

Mitogen-activated protein kinases (MAPKs) play vital roles in multiple cellular processes and represent prominently pursued targets for development of therapeutic regimes. The MAPK Spc1 (p38 homologue) is known to be very important for both mitotic promotion and delay in Schizosaccharomyces pombe. However, the mechanism responsible for mitotic inhibition has remained elusive. Cdc25 (Cdc2 activator) and Wee1 (Cdc2 inhibtor) are important determinants of mitotic timing in all eukaryotes. Our results show that Spc1 can sense the perturbations in the balance of Cdc25 and Wee1 activities in S. pombe and that its function as a mitotic inhibitor is very important for controlling the same. An Spc1–Srk1–Rad24-dependent pathway for mitotic inhibition has been reported earlier.Here we report the presence of an alternative mechanism wherein Spc1 targets the 14–3–3 protein, Rad24, independently of Srk1, leading to relocalization of Cdc25 and mitotic inhibition. Our observations suggest that this pathway can serve as a backup mechanism for Cdc2 inactivation in the absence of Wee1. Copyright © 2017 John Wiley & Sons, Ltd.

Yeast

The fission yeast MAPK Spc1 senses perturbations in Cdc25 and Wee1 activities and targets Rad24 to restore this balance

Progression into mitosis is a major point of regulation in the Schizosaccharomyces pombe cell cycle, and its proper control is essential for maintenance of genomic stability. Investigation of the G2/M progression event in S. pombe has revealed the existence of a complex regulatory process that is responsible for making the decision to enter mitosis. Newer aspects of this regulation are still being revealed. In this paper, we report the discovery of a novel mode of regulation of G2/M progression in S. pombe. We show that the mitogen-activated protein kinase (MAPK)-regulated transcription factor Atf1 is a regulator of Cdc13 (mitotic cyclin) transcription and is therefore a prominent player in the regulation of mitosis in S. pombe. We have used genetic approaches to study the effect of overexpression or deletion of Atf1 on the cell length and G2/M progression of S. pombe cells. Our results clearly show that Atf1 overexpression accelerates mitosis, leading to an accumulation of cells with shorter lengths. The previously known major regulators of entry into mitosis are the Cdc25 phosphatase and the Wee1 kinase, which modulate cyclin-dependent kinase (CDK) activity. The significantly striking aspect of our discovery is that Atf1-mediated G2/M progression is independent of both Cdc25 and Wee1. We have shown that Atf1 binds to the Cdc13 promoter, leading to activation of Cdc13 expression. This leads to enhanced nuclear localization of CDK Cdc2, thereby promoting the G2/M transition. © 2014, American Society for Microbiology. All Rights Reserved.

Eukaryotic Cell

The basic leucine zipper domain transcription factor Atf1 directly controls Cdc13 expression and regulates mitotic entry independently of wee1 and Cdc25 in Schizosaccharomyces pombe

Cigarette smoke has long been recognized as a major environmental pollutant that can cause significant damage to the cellular macromolecules. Although much is known about the types of damage, little is known about the cellular responses to the stress caused by cigarette smoke. We have used the fission yeast Schizosaccharomyces pombe to elucidate the overall cellular responses towards cigarette smoke. Here, we demonstrate that fission yeast cells exposed to aqueous extract of cigarette smoke exhibit cell cycle arrest and cell death in a dose-dependent manner. Cigarette smoke treatment also results in accumulation of reactive oxygen species, unusual nuclear morphology and altered cellular structure. Our data further establish activation of the S phase checkpoint in cigarette smoke-exposed Sz. pombe cells. The checkpoint proteins Rad3, Rad26, Rad17, Rad1, Hus1 and Cds1 play key roles in this process, as evidenced by cell survival and biochemical analysis, although another checkpoint protein, Rad9, seems to be less required. Our results also suggest involvement of the stress-activated protein kinase Spc1/Sty1 and the bZIP transcription factors Atf1 and Pap1 in the cellular response towards cigarette smoke extract. These findings indicate activation of the critical S phase checkpoint and cell cycle arrest in Sz, pombe following CSE assault. Copyright © 2005 John Wiley & Sons, Ltd.

Activation of S phase checkpoint by cigarette smoke extract in Schizosaccharomyces pombe

Our recent in vitro results [4] indicate that cigarette smoke induces oxidation of human plasma proteins and extensive oxidative degradation of the guinea pig lung, heart, and liver microsomal proteins, which is almost completely prevented by ascorbic acid. In this paper, we substantiate the in vitro results with in vivo observations. We demonstrate that exposure of subclinical or marginal vitamin C-deficient guinea pigs to cigarette smoke causes oxidation of plasma proteins as well as extensive oxidative degradation of the lung microsomal proteins. Cigarette smoke exposure also results in some discernible damage of the heart microsomal proteins. The oxidative damage has been manifested by SDS-PAGE, accumulation of carbonyl and bityrosine, as well as loss of tryptophan and protein thiols. Cigarette smoke exposure also induces peroxidation of microsomal lipids as evidenced by the formation of conjugated dienes, malondialdehyde, and fluorescent pigment. Cigarette smoke-induced oxidative damage of proteins and peroxidation of lipids are accompanied by marked drop in the tissue ascorbate levels. Protein damage and lipid peroxidation are also observed in cigarette smoke-exposed pair-fed guinea pigs receiving 5 mg vitamin C/animal/day. However, complete protection against protein damage and lipid peroxidation occurs when the guinea pigs are fed 15 mg vitamin C/animal/day. Also, the cigarette smoke- induced oxidative damage of proteins and lipid is reversed after discontinuation of cigarette smoke exposure accompanied by ascorbate therapy. The results, if extrapolated to humans, indicate that comparatively large doses of vitamin C may protect the smokers from cigarette smoke-induced oxidative damage and associated degenerative diseases. (C) 2000 Elsevier Science Inc.

Free Radical Biology and Medicine

Vitamin C prevents cigarette smoke-induced oxidative damage in vivo

Aqueous extract of cigarette smoke (CS) contains some stable oxidants, which oxidize human plasma proteins, bovine serum albumin, amino acid homopolymers, and also cause extensive oxidative degradation of microsomal proteins. Similar observations are made when the aqueous extract of cigarette smoke is replaced by whole phase CS solution or whole phase cigarette smoke. CS-induced microsomal protein degradation is a two step process: (i) oxidation of proteins by the oxidants present in the CS and (ii) rapid proteolytic degradation of the oxidized proteins by proteases present in the microsomes. Using aqueous extract of CS equivalent to that produced from one-twentieth of a cigarette, the observed initial and postcigarette smoke treated values of different parameters of oxidative damage per milligram of microsomal proteins are respectively: 0.24 and 1.74 nmoles for carbonyl formation, 125.4 and 62.8 fluorescence units for tryptophan loss, 10.2 and 33.4 fluorescence units for bityrosine formation, and 58.3 and 12.2 nmoles for loss of protein thiols. When compared with sodium dodecyl sulphate polyacrylamide gel electrophoresis profiles of untreated microsomal proteins, the extent of microsomal protein degradation after treatment with whole phase CS solution or aqueous extract of CS is above 90%. Ascorbate (100 μM) almost completely prevents cigarette smoke-induced protein oxidation and thereby protects the microsomes from subsequent proteolytic degradation. Glutathione is partially effective, but other antioxidants including superoxide dismutase, catalase, vitamin E, probucol, β-carotene, mannitol, thiourea, and histidine are ineffective. The gas phase cigarette smoke contains unstable reactive oxygen species such as superoxide (O2-.) and hydrogen peroxide (H2O2) that can cause substantial oxidation of pure protein like albumin but is unable to produce significant oxidative damage of microsomal proteins. Gas phase cigarette smoke-induced albumin oxidation is not only inhibited by ascorbate and glutathione but also by superoxide dismutase, catalase and mannitol. The stable oxidants in the cigarette smoke are not present in the tobacco and are apparently produced by the interaction of O2-./H2O2/OH. of the gas phase with some components of the tar phase during/following the burning of tobacco. Copyright (C) 1999 Elsevier Science Inc.

Journal	Data powered by TypesetCell Cycle
Publisher	Data powered by TypesetTaylor and Francis Inc.
ISSN	1538-4101
Open Access	No