Clinical and preclinical data reveal that RECQL5 protein overexpression in breast cancer was strongly correlated with poor prognosis, survival, and therapeutic resistance. In the current investigation, we report design, synthesis, and specificity of a small molecule, 4a, which can preferentially kill RECQL5-expressing breast cancers but not RECQL5 knockout. Our stringent analysis showed that compound 4a specifically sensitizes RECQL5-expressing cancers, while it did not have any effect on other members of DNA RECQLhelicases. Integrated approaches of organic synthesis, biochemical, in silico molecular simulation, knockouts, functional mutation, and rescue experiments showed that 4a potently inhibits RECQL5-helicase activity and stabilizes RECQL5-RAD51 physical interaction, leading to impaired HRR and preferential killing of RECQL5-expressing breast cancer. Moreover, 4a treatment led to the efficient sensitization of cisplatin-resistant breast cancers but not normal mammary epithelial cells. Pharmacologically, compound 4a was orally effective in reducing the growth of RECQL5-expressing breast tumors (human xenograft) in NUDE-mice with no appreciable toxicity to the vital organs.

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DRA0282, a hypothetical protein, was found in a pool of nucleotide-binding proteins in Deinococcus radiodurans cells recovering from gamma radiation stress. This pool exhibited an unusual inhibition of nuclease activity by ATP. The N terminus of DRA0282 showed similarity to human Ku80 homologues, while the C terminus showed no similarities to known proteins. The recombinant protein required Mn 2+ for its interaction with DNA and protected dsDNA from exonuclease III degradation. The binding of the protein to supercoiled DNA with a K d of~2.93 nM was nearly 20-fold stronger than its binding to ssDNA and nearly 67-fold stronger than its binding to linear dsDNA. Escherichia coli cells expressing DRA0282 showed a RecA-dependent enhancement of UV and gamma radiation tolerance. The DdrA0282 mutant of D. radiodurans showed a dose-dependent response to gamma radiation. At 14 kGy, the DdrA0282 mutant showed nearly 10-fold less survival, while at this dose both pprA : : catDdrA0282 and pprA : : cat mutants were nearly 100-fold more sensitive than the wild-type. These results suggested that DRA0282 is a DNA-binding protein with a preference for superhelical DNA, and that it plays a role in bacterial resistance to DNA damage through a pathway in which PprA perhaps plays a dominant role in D. radiodurans. INTRODUCTIONDeinococcus radiodurans R1 shows extraordinary tolerance to several abiotic stresses, including ionizing and nonionizing radiation (Makarova et al., 2001;Cox & Battista 2005;Blasius et al., 2008). This bacterium possesses an efficient DNA double-strand break (DSB) repair mechanism (Minton, 1994;Daly & Minton, 1996) and strong oxidative stress tolerance mechanisms (Markillie et al., 1999; Daly et al., 2004Daly et al., , 2007. DSB repair in this organism displays RecA-dependent biphasic kinetics (Daly et al., 1994;Slade et al., 2009). Phase I involves extended synthesis-dependent strand annealing (ESDSA) processes (Zahradka et al., 2006), followed by the second phase of the maturation of individual chromosomes, which presumably involves homologous recombination (Daly & Minton, 1996). The D. radiodurans R1 genome (White et al., 1999) shows the absence of recBC and sbcB/sbcA genes, while the recD2 protein (Montague et al., 2009) and components of the complete RecF pathway are present (Blasius et al., 2008). Expression of sbcB (Misra et al., 2006) and recBC (Khairnar et al., 2008) genes of Escherichia coli in D. radiodurans makes this bacterium sensitive to gamma radiation by delaying its DSB repair, further supporting the contention that the RecF recombination pathway contributes to DSB repair and radiation resistance in this bacterium. The role of the RecFOR pathway in DSB repair through an ESDSA mechanism has been suggested in D. radiodurans (Bentchikou et al., 2010). However, the significance of DNA protection in radiation resistance and DSB repair during the early phase of post-irradiation recovery (PIR) has also been shown. Two proteins, namely DdrA (Harris et al., 2004) and PprA (Narumi et al., 2004), have bee...

Pasteurella multocida has been recognized as an important veterinary pathogen for over a century. Conventional methods for diagnosis of pasteurellosis rely on the detection of the organism by microscopy and its isolation and identification. However, as far as pasteurellosis is concerned, it is not just sufficient to know the identity of the organism. To constitute effective control measures, it is important to know the serotype of the organism. A study was undertaken to characterize the Pasteurella isolates from local pigs in India with clinical respiratory disease by determination of their capsule types and presence or absence of toxin gene. Pasteurella could be isolated from 66.70% of pigs with clinical respiratory disease. All the isolates were confirmed through biochemical characterization and P. multocida-specific polymerase chain reaction. It has also been observed that all the isolates belonged to capsular type D. All the isolates were sensitive to chloramphenicol, chlortetracycline, doxycycline, and enrofloxacin, while the rest of the antibiotics were less effective. It has also been observed that all isolates were resistant to cephalexin, penicillin G, and sulphadiazine. The study revealed the detection of P. multocida serotype D from clinical respiratory diseases of local pigs of India, which could be one of the important respiratory tract pathogens responsible for mortality of local pigs in India.