FANCD2-dependent mitotic DNA synthesis relies on PCNA K164 ubiquitination

Ubiquitination of proliferating cell nuclear antigen (PCNA) at lysine 164 (K164) activates DNA damage tolerance pathways. Currently, we lack a comprehensive understanding of how PCNA K164 ubiquitination promotes genome stability. To evaluate this, we generated stable cell lines expressing PCNAK164R from the endogenous PCNA locus. Our data reveal that the inability to ubiquitinate K164 causes perturbations in global DNA replication. Persistent replication stress generates under-replicated regions and is exacerbated by the DNA polymerase inhibitor aphidicolin. We show that these phenotypes are due, in part, to impaired Fanconi anemia group D2 protein (FANCD2)-dependent mitotic DNA synthesis (MiDAS) in PCNAK164R cells. FANCD2 mono-ubiquitination is significantly reduced in PCNAK164R mutants, leading to reduced chromatin association and foci formation, both prerequisites for FANCD2-dependent MiDAS. Furthermore, K164 ubiquitination coordinates direct PCNA/FANCD2 colocalization in mitotic nuclei. Here, we show that PCNA K164 ubiquitination maintains human genome stability by promoting FANCD2-dependent MiDAS to prevent the accumulation of under-replicated DNA.

Mitotic DNA Synthesis in Untransformed Human Cells Preserves Common Fragile Site Stability via a FANCD2-Driven Mechanism That Requires HELQ

Faithful genome duplication is a challenging task for dividing mammalian cells, particularly under replication stress where timely resolution of late replication intermediates (LRIs) becomes crucial prior to cell division. In human cancer cells, mitotic DNA repair synthesis (MiDAS) is described as a final mechanism for the resolution of LRIs to avoid lethal chromosome mis-segregation. RAD52-driven MiDAS achieves this mission in part by generating gaps/breaks on metaphase chromosomes, which preferentially occur at common fragile sites (CFS). We previously demonstrated that a MiDAS mechanism also exists in untransformed and primary human cells, which is RAD52 independent but requires FANCD2. However, the properties of this form of MiDAS are not well understood. Here, we report that FANCD2-driven MiDAS in untransformed human cells: 1) requires a prerequisite step of FANCD2 mono-ubiquitination by a subset of Fanconi anemia (FA) proteins, 2) primarily acts to preserve CFS stability but not to prevent chromosome mis-segregation, and 3) depends on HELQ, which potentially functions at an early step. Hence, FANCD2-driven MiDAS in untransformed cells is built to protect CFS stability, whereas RAD52-driven MiDAS in cancer cells is likely adapted to prevent chromosome mis-segregation at the cost of CFS expression. Notably, we also identified a novel form of MiDAS, which surfaces to function when FANCD2 is absent in untransformed cells. Our findings substantiate the complex nature of MiDAS and a link between its deficiencies and the pathogenesis of FA, a human genetic disease.

Normal values of knee angle, intercondylar and intermalleolar distances in Nigerian children

There is little data on the range of variation of knee angle, intermalleolar and intercondylar distances in African children. Such measurements are needed to assist determining whether a child legs are normal or not. Knee angle intermalleolar and intercondylar distances were measured in 2166 Nigerian children aged one year to 10 years to establish normal values for these measurements. In the study we discovered that knees were maximally bowed at ages 1-3 years and reduced to neutral of 0 degrees at age five (5 years) in girls and age seven (7) in boys. Both sexes had no bowing after age (7 years) in boys. Both sexes had no bowing after age of 7 years. The valgus angle was found to be constant at about 11 degrees between ages 1-10 years in both sexes. Mean intercondylar distance was 0.2 cm at 1 year of age and did not vary significantly at 10 years of age. The greatest intermalleolar distances of 2.5 cm and 2.2 cm were noted between the ages of 2 and 4 years. Normograms of these measurements are presented as diagnostic aids in clinical settings.

Pharmacological effects of the giant African snail Achatina fulica

The body fluid and tissue extract of the foot of Achatina fulica, the edible giant African snail, were investigated and quantified for pharmacological effects. Both reduced spontaneous locomotor activity in mice, protected them from death from amphetamine induced toxicity, prolonged hexobarbitone sleeping time and caused a depletion of catecholamines from various organs of the rat. From this a central depressant action combined with an antihypertensive effect is inferred. This is in keeping with the objectives of local traditional healers who use the snail on their patients. It is suggested that eledoison, a potent antihypotensive agent found in aquatic snails may also be present in terrestrial snails such as Achatina.

Preliminary studies on nasal decongestant activity from the seed of the shea butter tree, Butyrospermum parkii

1 The seed of Butyrospermum parkii yields shea butter which according to local traditional healers relieves inflammation of the nostrils. 2 Since there is as yet no absolutely satisfactory nasal decongestant in clinical use, it was decided to investigate the effects of shea butter in nasal congestion. The substance was prepared in the laboratory. 3 The human subjects used were those suffering from rhinitis with moderate to severe nasal congestion. They were divided into the test group which received shea butter, the control group which was treated with xylometazoline and the 'placebo' group which received white petroleum jelly B.P. 4 The results showed that nasal congestion was relieved more satisfactorily in the test group than in the other two groups. 5 It is concluded that shea butter may prove more efficacious in nasal congestion than conventional nasal drops.