Bacteria-borne antidote for cancer

http://www.nature.com/nindia/2010/100802/full/nindia.2010.105.html

doi:10.1038/nindia.2010.105; Published online 2 August 2010

Researchers have isolated a new organic compound that halts the migration of cancer cells. They found the compound in a species of Streptomyces, a type of bacteria known to yield antibiotics¹.

The compound inhibited the migration of cultured human and mouse cancer cells by blocking the activity of cysteine protease, an enzyme whose level increases in cancer cells. This suggests that the compound could be a potential drug for treating cancer.

To hunt down effective inhibitors of this enzyme, the researchers screened severalStreptomyces species by exposing them to high-protein-growth media.

They found one strain of Streptomyces species — NCIM 2081 — with protease inhibitory effect. They isolated the active compound CPI-2081 — a mixture of two novel pentapeptides — from the bacteria. The compound's inhibitory effect against migration of cancer cells was tested using human breast and skin cancer cells and mouse skin cancer cells.

The compound successfully inhibited migration of human breast and mouse skin cancer cells at concentrations lower than the cytotoxic dose.

The study is significant since the compound could be developed as a complementary therapy to existing anticancer drugs, which have harmful side effects due to non-specific action on non-cancerous host tissues. The researchers say spread of a tumour (metastasis) can be restricted by applying CPI-2081, followed by antitumour drugs.

The authors of this study are from: National Chemical Laboratory & National Centre for Cell Science, Pune, India; Yale University School of Medicine, New Haven, Connecticut, USA; Memorial Sloan Kettering Cancer Center (MSKCC), New York, USA and CEA Grenoble, LEMOH/INAC/SPrAM, Grenoble, France.

• References

  1. Singh, P. J. et al. Isolation, structure, and functional elucidation of a modified pentapeptide, cysteine protease inhibitor (CPI-2081) from Streptomyces species 2081 that exhibit inhibitory effect on cancer cell migration. J. Med. Chem. 53, 5121-5128 (2010) | Article | PubMed

Guardian of genome: Protein helps prevent damaged DNA in yeast

http://www.eurekalert.org/pub_releases/2010-08/cu-ot073010.php

Like a scout that runs ahead to spot signs of damage, a protein in yeast safeguards the yeast cell’s genome during replication.

Researchers from Cornell University’s Weill Institute for Cell and Molecular Biology have discovered how a protein called Mec1 plays the role of “guardian of the genome”, explained Marcus Smolka, assistant professor of molecular biology and genetics. The findings, “DNA Damage Signalling Recruits the Rtt 107-Six4 Scaffolds via Dpb11 to Mediate Replication Stress Response,” published in Jornal Molecualar Cell, July 30,2010.

Previous Studies have shown that cells lacking Mec1 accumulate damaged DNA and become more sensitive to agents that interfere with replication. The researchers report that the Mec1 protein monitors and repairs the machinery responsible for replicating the DNA. At times, when DNA becomes damaged, the replication machinery can actually detach from the DNA, but Mec1 coordinates the repair of the machinery and the DNA itself, allowing it to restart and continue replicating.

“Mec1 organize the cell’s response against things that jeopardize the integrity of the genome,” Smolka said.

During replication process, Mec1 accumulates at trouble spots such as lesions in the DNA or other blocks to replication. Mec1 is know as a kinase, a type of enzyme that modifies other proteins by adding a phosphate group to them, phosphorylation, which then leads to functional change in the protein. Mec1 adds a phosphate group to a protein known as Six4, which then triggers Six4 to anchor to the replication machinery. Six4 then can employ a variety of tools to repair DNA and the replication machinery.

The findings are important because researchers have discovered  counterparts, orthologues to Mec1 & related proteins with similar biological pathways in humans. Also, mutations to the human genes that produce Mec1 and related proteins can lead to cancer predisposition and neurological disorders.At the same time, cancer cells employ their own similar replication repair system.

Recently, other researchers discovered that the human version of Mec1 called ATR, phosphorylates a protein that is the human counterpart to Six4. The next step, Smolka said, will be to see if after phosphorylation the human Six4 also anchors to the replication machinery to repair any damaged machinery or DNA.

Gain of function of mutant p53: The mutant p53/NF-Y protein complex reveals an aberrant transcriptional mechanism of cell cycle regulation

Cancer Cell, Volume 10, Issue 3, 1 September 2006, Pages 191-202
Silvia Di Agostino, Sabrina Strano, Velia Emiliozzi, Valentina Zerbini, Marcella Mottolese, Ada Sacchi, Giovanni Blandino and Giulia Piaggio

Summary

• This article investigates the mechanistic aspects of mutant p53 gain of function in response to DNA damage. We show that mutant forms of p53 protein interact with NF-Y.
  
• The expression of cyclin A, cyclin B1, cdk1, and cdc25C, as well as the cdk1-associated kinase activities, is upregulated after DNA damage, provoking a mutant p53/NF-Y-dependent increase in DNA synthesis.
  
• Mutant p53 binds NF-Y target promoters and, upon DNA damage, recruits p300, leading to histone acetylation. The recruitment of mutant p53 to the CCAAT sites is severely impaired upon abrogation of NF-YA expression.
  
• Endogenous NF-Y, mutant p53, and p300 proteins form a triple complex upon DNA damage. We demonstrate that aberrant transcriptional regulation underlies the ability of mutant p53 proteins to act as oncogenic factors.

• NF-Y is an ubiquitous heteromeric CCAAT-binding protein composed of three subunits, NF-YA, NF-YB, NF-YC, all necessary for DNA-binding.

• NF-Y sequences are available from several species: the NF-YA gene is cloned from man, rat, mouse, S. pombe, Brassica napus, Schistosoma mansoni and sea urchin (38-41); NF-YB from Kluyveromyces lactis, Aspergillus nidulans, Zea mais, lamprey, Xenopus, and chicken.

• Each of the three subunits displays highly conserved domains in all species. The NF-YA homology domain can be sharply divided into subunit-association and DNA-contacting subdomains. NF-YB and NF-YC tight association is a prerequisite for NF-YA binding and sequence-specific DNA interactions.

• Both NF-YB and NF-YC conserved domains contain putative histone fold motifs. This motif, common to all core histones, is composed of three a-helices separated by short loops/strand regions. NF-YA and NF-YC contain activation domains rich in Glutamines and hydrophobic residues.

ERK-MAPK signaling opposes Rho-kinase to promote endothelial cell survival and sprouting during angiogenesis

Cancer Cell, Volume 9, Issue 1, 1 January 2006, Pages 33-44
Georgia Mavria, Yvonne Vercoulen, Maggie Yeo, Hugh Paterson, Maria Karasarides, Richard Marais, Demelza Bird and Christopher J. Marshall

Summary

Inhibition of ERK-MAPK signaling by expression of dominant-negative MEK1 in the tumor vasculature suppresses angiogenesis and tumor growth. In an organotypic tissue culture angiogenesis assay, ERK-MAPK inhibition during the migratory phase results in loss of bipolarity, detachment, and cell death of isolated endothelial cells and retraction of sprouting tubules. These effects are the consequence of upregulated Rho-kinase signaling. Transient inhibition of Rho-kinase rescues the effects of ERK-MAPK inhibition in vitro and in vivo, promotes sprouting, and increases vessel length in tumors. We propose a regulatory role of Rho-kinase by ERK-MAPK during angiogenesis that acts through the control of actomyosin contractility. Our data delineate a mechanism by which ERK-MAPK promotes endothelial cell survival and sprouting by downregulating Rho-kinase signaling.