Biomedical subjects

Alicia Bravo

Publications and source records attributed to Alicia Bravo.

5 recordsLinked to original sources

PubMed2006

A uracil-DNA glycosylase inhibitor encoded by a non-uracil containing viral DNA.

Uracil-DNA glycosylase (UDG) is an enzyme involved in the base excision repair pathway. It specifically removes uracil from both single-stranded and double-stranded DNA. The genome of the Bacillus subtilis phage 29 is a linear double-stranded DNA with a terminal protein covalently linked at each 5'-end. Replication of 29 DNA starts by a protein-priming mechanism and generates intermediates that have long stretches of single-stranded DNA. By using in vivo chemical cross-linking and affinity chromatography techniques, we found that UDG is a cellular target for the early viral protein p56. Addition of purified protein p56 to B. subtilis extracts inhibited the endogenous UDG activity. Moreover, extracts from 29-infected cells were deficient in UDG activity. We suggested that inhibition of the cellular UDG is a defense mechanism developed by 29 to prevent the action of the base excision repair pathway if uracil residues arise in their replicative intermediates. Protein p56 is the first example of a UDG inhibitor encoded by a non-uracil-containing viral DNA.

Bacillus Phages↗

PubMed2005

A new plasmid vector for regulated gene expression in Bacillus subtilis.

We have developed a novel regulated expression vector for Bacillus subtilis based on the Staphylococcus aureus plasmid pUB110. This vector, named pPR54, carries the P(R) promoter and the cI857 gene (encoding a temperature-sensitive transcriptional repressor) from the Escherichia coli phage lambda. Using the gfp gene from the jellyfish Aequorea victoria as a reporter, we show that pPR54 is a useful vector for controllable production of heterologous proteins in B. subtilis.

Bacillus subtilis↗

PubMed2005

Compartmentalization of prokaryotic DNA replication.

It becomes now apparent that prokaryotic DNA replication takes place at specific intracellular locations. Early studies indicated that chromosomal DNA replication, as well as plasmid and viral DNA replication, occurs in close association with the bacterial membrane. Moreover, over the last several years, it has been shown that some replication proteins and specific DNA sequences are localized to particular subcellular regions in bacteria, supporting the existence of replication compartments. Although the mechanisms underlying compartmentalization of prokaryotic DNA replication are largely unknown, the docking of replication factors to large organizing structures may be important for the assembly of active replication complexes. In this article, we review the current state of this subject in two bacterial species, Escherichia coli and Bacillus subtilis, focusing our attention in both chromosomal and extrachromosomal DNA replication. A comparison with eukaryotic systems is also presented.

Bacillus subtilis↗

PubMed2004

Targeted inhibition of galectin-1 gene expression in tumor cells results in heightened T cell-mediated rejection; A potential mechanism of tumor-immune privilege.

Despite the existence of tumor-specific immune cells, most tumors have devised strategies to avoid immune attack. We demonstrate here that galectin-1 (Gal-1), a negative regulator of T cell activation and survival, plays a pivotal role in promoting escape from T cell-dependent immunity, thus conferring immune privilege to tumor cells. Blockade of immunosuppressive Gal-1 in vivo promotes tumor rejection and stimulates the generation of a tumor-specific T cell-mediated response in syngeneic mice, which are then able to resist subsequent challenge with wild-type Gal-1-sufficient tumors. Our data indicate that Gal-1 signaling in activated T cells constitutes an important mechanism of tumor-immune escape and that blockade of this inhibitory signal can allow for and potentiate effective immune responses against tumor cells, with profound implications for cancer immunotherapy.

Animals↗

PubMed2003

In vivo assembly of phage phi 29 replication protein p1 into membrane-associated multimeric structures.

The mechanisms underlying compartmentalization of prokaryotic DNA replication are largely unknown. In the case of the Bacillus subtilis phage 29, the viral protein p1 enhances the rate of in vivo viral DNA replication. Previous work showed that p1 generates highly ordered structures in vitro. We now show that protein p1, like integral membrane proteins, has an amphiphilic nature. Furthermore, immunoelectron microscopy studies reveal that p1 has a peripheral subcellular location. By combining in vivo chemical cross-linking and cell fractionation techniques, we also demonstrate that p1 assembles in infected cells into multimeric structures that are associated with the bacterial membrane. These structures exist both during viral DNA replication and when 29 DNA synthesis is blocked due to the lack of viral replisome components. In addition, protein p1 encoded by plasmid generates membrane-associated multimers and supports DNA replication of a p1-lacking mutant phage, suggesting that the pre-assembled structures are functional. We propose that a phage structure assembled on the cell membrane provides a specific site for 29 DNA replication.

Amino Acid Sequence↗