The intra-S phase checkpoint targets Dna2 to prevent stalled replication forks from reversing

When replication forks stall at damaged bases or upon nucleotide depletion, the intra-S phase checkpoint ensures they are stabilized and can restart. In intra-S checkpoint-deficient budding yeast, stalling forks collapse, and ～10% form pathogenic chicken foot structures, contributing to incomplete replication and cell death (Lopes et al., 2001; Sogo et al., 2002; Tercero and Diffley, 2001). Using fission yeast, we report that the Cds1(Chk2) effector kinase targets Dna2 on S220 to regulate, both in vivo and in vitro, Dna2 association with stalled replication forks in chromatin. We demonstrate that Dna2-S220 phosphorylation and the nuclease activity of Dna2 are required to prevent fork reversal. Consistent with this, Dna2 can efficiently cleave obligate precursors of fork regression-regressed leading or lagging strands-on model replication forks. We propose that Dna2 cleavage of regressed nascent strands prevents fork reversal and thus stabilizes stalled forks to maintain genome stability during replication stress.     

Lagerstroemia menglaensis sp. nov. (Lythraceae) from Xishuangbanna,Yunnan Province,China

Lagerstroemia menglaensis C. H. Gu, M. C. Ji & D. D. Ma, a new species of Lythraceae from Xishuangbanna, Yunnan, China is described and illustrated. The morphological characteristics of the new species and two morphologically similar species (L. guilinensis and L. venusta) are compared, and a key to distinguish between them is provided.     

Primulina xiziae sp. nov. (Gesneriaceae) from Zhejiang Province,China

A new species of Gesneriaceae, Primulina xiziae Fang Wen, Yue Wang & G. J. Hua, from Zhejiang Province, China, is identified, illustrated and described. It resembles the widespread P. eburnea, and the stenochoric P. pseudoeburnea, but differs by the leaf blades being ovate‐elliptic or ovate, chartaceous with ciliate margins, 8.5–13.8 mm long, slender peduncle, ovate, ca 1.2 × 1.0 cm large bracts that are generally withered but persistent before full‐blooming stage, slender tubular‐infundibuliform, ca 25.0 × 7.5 mm corolla tube, limb lobes with acute apices, 3 staminodes, and by forming a dormancy bud in winter.     

Micropera tibetica sp. nov. (Orchidaceae) from southeastern Tibet,China

A new species of Orchidaceae, Micropera tibetica from Medog County, Tibet, China, is described and illustrated. It is morphologically similar to M. mannii, from which it differs by having creamy white flowers, not twisted column, strongly oblique lateral sepals with emarginated apex, and very small lateral lobes of the lip.     

Ultrasonic-assisted extraction of polysaccharides from Hohenbuehelia serotina by response surface methodology

An ultrasonic-assisted procedure for the extraction of polysaccharides from the fruiting body of Hohenbuehelia serotina was investigated using response surface methodology. The effects of four factors on the yield of polysaccharides were studied. The optimized conditions were extraction temperature 94°C, extraction time 3.0h, ratio of water to raw material 110:1 and ultrasonic power 480W. Under these conditions, the experimental yield of polysaccharides was 17.45±0.18%, which was well matched with the predictive yield of 17.54%. The molecular weight of polysaccharide was ranged from 1.19×10(3) to 1.55×10(4)Da. The polysaccharides were composed of ribose, arabinose, mannose, glucose and galactose in a ratio of 0.65:0.69:9.35:14.24:5.47. Then, the structural features of untreated materials, hot water extraction residue and ultrasonic-assisted extraction residue were compared by SEM. Results indicated that ultrasonic-assisted extraction technology could be an effective and advisable technique.     

Progesterone and low-dose vitamin D hormone treatment enhances sparing of memory following traumatic brain injury

Progesterone (PROG) has been shown to protect the brain from traumatic injury and is now in Phase III clinical trials. Our work shows that PROG's beneficial effects can be reduced in vitamin D hormone (VDH)-deficient subjects. VDH can modulate neuronal apoptosis, trophic factors, inflammation, oxidative stress, excitotoxicity, and myelin and axon repair. We investigated whether VDH combined with PROG could improve behavioral outcomes more than PROG alone in VDH-sufficient rats given bilateral contusions of the medial frontal cortex. PROG and different doses of VDH (1 μg/kg, VDH1; 2.5 μg/kg, VDH2; 5 μg/kg, VDH3) were injected intraperitoneally 1 h post-injury. Eight additional doses of PROG were given subcutaneously over 8 days with tapering over the last 2 days. Neurobehavioral tests, necrotic cavity, neuronal death and activation of astrocytes were evaluated 21 days post-injury. We found that PROG and PROG + VDH preserve spatial memory processing. VDH1 + PROG improved performance in acquisition more effectively than PROG alone, indicating that the low VDH dose is optimal for combination therapy. There were no significant differences in necrotic cavity size among the groups. The density of positive staining for reactive astrocytes (glial fibrillary acidic protein (GFAP)) increased and the cell bodies and processes of GFAP-positive cells were enlarged in the PROG + VDH1 group. Our data indicate that the combination of PROG and VDH is more effective than PROG alone in preserving spatial and reference memory, and that PROG plus low-dose VDH can activateGFAP reactions up to 21 days after injury. This effect may be one of the mechanisms underlying PROG's neuroprotective effects in combination with VDH.     

Whole-Genome Sequence of Staphylococcus hominis, an Opportunistic Pathogen

Staphylococcus hominis is a commensal coagulase-negative species of staphylococci. It has been considered a presumptive and opportunistic pathogen that causes nosocomial infections in humans. Here we present the draft genome sequence of S. hominis ZBW5, a multidrug-resistant strain isolated from a human skin sample, which provides opportunities to understand the mechanism and genetic basis of its pathogenesis.     

Molecular mechanisms of chromium in alleviating insulin resistance

Type 2 diabetes is often associated with obesity, dyslipidemia and cardiovascular anomalies and is a major health problem approaching global epidemic proportions. Insulin resistance, a prediabetic condition, precedes the onset of frank type 2 diabetes and offers potential avenues for early intervention to treat the disease. Although lifestyle modifications and exercise can reduce the incidence of diabetes, compliance has proved to be difficult, warranting pharmacological interventions. However, most of the currently available drugs that improve insulin sensitivity have adverse effects. Therefore, attractive strategies to alleviate insulin resistance include dietary supplements. One such supplement is chromium, which has been shown to reduce insulin resistance in some, but not all, studies. Furthermore, the molecular mechanisms of chromium in alleviating insulin resistance remain elusive. This review examines emerging reports on the effect of chromium, as well as molecular and cellular mechanisms by which chromium may provide beneficial effects in alleviating insulin resistance.     

Elongator complex is critical for cell cycle progression and leaf patterning in Arabidopsis

The mitotic cell cycle in higher eukaryotes is of pivotal importance for organ growth and development. Here, we report that Elongator, an evolutionarily conserved histone acetyltransferase complex, acts as an important regulator of mitotic cell cycle to promote leaf patterning in Arabidopsis. Mutations in genes encoding Elongator subunits resulted in aberrant cell cycle progression, and the altered cell division affects leaf polarity formation. The defective cell cycle progression is caused by aberrant DNA replication and increased DNA damage, which activate the DNA replication checkpoint to arrest the cell cycle. Elongator interacts with proliferating cell nuclear antigen (PCNA) and is required for efficient histone 3 (H3) and H4 acetylation coupled with DNA replication. Levels of chromatin-bound H3K56Ac and H4K5Ac known to associate with replicons during DNA replication were reduced in the mutants of both Elongator and chromatin assembly factor 1 (CAF-1), another protein complex that physically interacts with PCNA for DNA replication-coupled chromatin assembly. Disruptions of CAF-1 also led to severe leaf polarity defects, which indicated that Elongator and CAF-1 act, at least partially, in the same pathway to promote cell cycle progression. Collectively, our results demonstrate that Elongator is an important regulator of mitotic cell cycle, and the Elongator pathway plays critical roles in promoting leaf polarity formation.