Functions and regulation of the APOBEC family of proteins.

APOBEC1 is a cytidine deaminase that edits messenger RNAs and was the first enzyme in the APOBEC family to be functionally characterized. Under appropriate conditions APOBEC1 also deaminates deoxycytidine in single-stranded DNA (ssDNA). The other ten members of the APOBEC family have not been fully characterized however several have deoxycytidine deaminase activity on ssDNAs. Despite the nucleic acid substrate preferences of different APOBEC proteins, a common feature appears to be their intrinsic ability to bind to RNA as well as to ssDNA. RNA binding to APOBEC proteins together with protein-protein interactions, post-translation modifications and subcellular localization serve as biological modulators controlling the DNA mutagenic activity of these potentially genotoxic proteins.

Association between the Thr431Asn polymorphism of the ROCK2 gene and risk of developing metastases of breast cancer.

The objective of this study was to analyze the genotype distributions and allele frequencies for ROCK2 Thr431Asn and Arg83Lys polymorphisms among breast cancer patients. In this case-control study, 223 patients with breast cancer were recruited and divided into two groups according to metastases (n = 128) and without metastases (n = 95). Genomic DNA from the patients and the control cases (n = 150) was analyzed by real-time PCR using a Light-Cycler. Neither genotype distributions nor the allele frequencies for the Arg83Lys polymorphism showed a significant difference between the groups. Although no marked changes were observed with nonmetastatic group, a statistically significant association was found between the control and metastatic group for the Thr431Asn polymorphism. Although homozygous carriers of the Thr431Thr genotype were more frequent, heterozygous carriers of the Thr431Asn genotype were less frequent among the metastatic patients than among controls. There was also an increase in Thr431 allele (60.5% in patients vs. 51.7% in controls) and decrease in Asn431 allele frequencies (48.3% in control vs. 39.5% in metastatic patients) in metastatic groups (p = 0.036). Our results demonstrate that Thr431Asn polymorphism of the ROCK2 gene could be a risk factor for the metastases of the breast cancer, and may help in predicting the prognosis.

Inhibition of Tropomyosin Receptor Kinase A Signaling Negatively Regulates Megakaryopoiesis and induces Thrombopoiesis.

Neurotrophin signaling modulates the differentiation and function of mature blood cells. The expression of neurotrophin receptors and ligands by hematopoietic and stromal cells of the bone marrow indicates that neurotrophins have the potential to regulate hematopoietic cell fate decisions. This study investigates the role of neurotrophins and Tropomyosin receptor kinases (Trk) in the development of megakaryocytes (MKs) and their progeny cells, platelets. Results indicate that primary human MKs and MK cells lines, DAMI, Meg-01 and MO7e express TrkA, the primary receptor for Nerve Growth Factor (NGF) signaling. Activation of TrkA by NGF enhances the expansion of human MK progenitors (MKPs) and, to some extent, MKs. Whereas, inhibition of TrkA receptor by K252a leads to a 50% reduction in the number of both MKPs and MKs and is associated with a 3-fold increase in the production of platelets. In order to further confirm the role of TrkA signaling in platelet production, TrkA deficient DAMI cells were generated using CRISPR-Cas9 technology. Comparative analysis of wild-type and TrkA-deficient Dami cells revealed that loss of TrkA signaling induced apoptosis of MKs and increased platelet production. Overall, these findings support a novel role for TrkA signaling in platelet production and highlight its potential as therapeutic target for Thrombocytopenia.