Learning, Life, and Lactation: Knowledge of Breastfeeding's Impact on Breast Cancer Risk Reduction and Its Influence on Breastfeeding Practices.

Introduction: The protective effects of breastfeeding against developing breast cancer are well known; however, it is unknown whether women are aware of this breastfeeding benefit. Research Aim/Questions: The aim of this investigation was to determine whether mothers received information about breast cancer risk reduction during breastfeeding counseling and whether this knowledge affected their decision to initiate and sustain breastfeeding. Materials and Methods: The survey was conducted at The Ohio State University Comprehensive Cancer Center with women aged 18-50 who had at least one live birth. Participants were recruited through primary care practice and a national clinical research registry. Results: Six hundred sixty-seven (92%) of the 724 respondents breastfed. Over half of them (56%), that is, 407 women (60.4% Caucasian, 46.9% African American), were aware before their most recent childbirth that breastfeeding reduced the risk of breast cancer. Of the 407 women, 36.4% said this knowledge affected their decision to breastfeed. Of the 39 who did not breastfeed, 23 women (59.0%) responded that awareness of risk reduction would have influenced their decision to breastfeed. Only 120 of 724 respondents (16.6%) received this information from healthcare providers. Women with this knowledge breastfed longer than those without this knowledge (13.2 versus 9.3 months; p < 0.001). More Caucasian women (76.4%) breastfed any one child for more than 6 months compared with African American women (63.2%; p = 0.011; chi-squared test). Conclusion: While several factors affect the initiation and duration of breastfeeding, this study demonstrates that knowledge of association between breastfeeding and breast cancer risk reduction may influence breastfeeding practices. Our study illustrates the need for improved counseling for mothers by healthcare providers regarding this benefit.

Characterization of Candida albicans RNA triphosphatase and mutational analysis of its active site.

The RNA triphosphatase component (CaCet1p) of the mRNA capping apparatus of the pathogenic fungus Candida albicans differs mechanistically and structurally from the RNA triphosphatase of mammals. Hence, CaCet1p is an attractive antifungal target. Here we identify a C-terminal catalytic domain of CaCet1p from residue 257 to 520 and characterize a manganese-dependent and cobalt-dependent NTPase activity intrinsic to CaCet1p. The NTPase can be exploited to screen in vitro for inhibitors. The amino acids that comprise the active site of CaCet1p were identified by alanine-scanning mutagenesis, which was guided by the crystal structure of the homologous RNA triphosphatase from Saccharomyces cerevisiae (Cet1p). Thirteen residues required for the phosphohydrolase activity of CaCet1p (Glu287, Glu289, Asp363, Arg379, Lys396, Glu420, Arg441, Lys443, Arg445, Asp458, Glu472, Glu474 and Glu476) are located within the hydrophilic interior of an eight-strand beta barrel of Cet1p. Each of the eight strands contributes at least one essential amino acid. The essential CaCet1p residues include all of the side chains that coordinate manganese and sulfate (i.e., gamma phosphate) in the Cet1p product complex. These results suggest that the active site structure and catalytic mechanism are conserved among fungal RNA triphosphatases.

Yeast homologues of tomosyn and lethal giant larvae function in exocytosis and are associated with the plasma membrane SNARE, Sec9.

We have identified a pair of related yeast proteins, Sro7p and Sro77p, based on their ability to bind to the plasma membrane SNARE (SNARE) protein, Sec9p. These proteins show significant similarity to the Drosophila tumor suppressor, lethal giant larvae and to the neuronal syntaxin-binding protein, tomosyn. SRO7 and SRO77 have redundant functions as loss of both gene products leads to a severe cold-sensitive growth defect that correlates with a severe defect in exocytosis. We show that similar to Sec9, Sro7/77 functions in the docking and fusion of post-Golgi vesicles with the plasma membrane. In contrast to a previous report, we see no defect in actin polarity under conditions where we see a dramatic effect on secretion. This demonstrates that the primary function of Sro7/77, and likely all members of the lethal giant larvae family, is in exocytosis rather than in regulating the actin cytoskeleton. Analysis of the association of Sro7p and Sec9p demonstrates that Sro7p directly interacts with Sec9p both in the cytosol and in the plasma membrane and can associate with Sec9p in the context of a SNAP receptor complex. Genetic analysis suggests that Sro7 and Sec9 function together in a pathway downstream of the Rho3 GTPase. Taken together, our studies suggest that members of the lethal giant larvae/tomosyn/Sro7 family play an important role in polarized exocytosis by regulating SNARE function on the plasma membrane.