BRCA1 regulates the G2/M checkpoint by activating Chk1 kinase upon DNA damage

The breast cancer tumor-suppressor gene, BRCA1, encodes a protein with a BRCT domain-a motif that is found in many proteins that are implicated in DNA damage response and in genome stability. Phosphorylation of BRCA1 by the DNA damage-response proteins ATM, ATR and hCds1/Chk2 changes in response to DNA damage and at replication-block checkpoints. Although cells that lack BRCA1 have an abnormal response to DNA damage, the exact role of BRCA1 in this process has remained unclear. Here we show that BRCA1 is essential for activating the Chk1 kinase that regulates DNA damage-induced G2/M arrest. Thus, BRCA1 controls the expression, phosphorylation and cellular localization of Cdc25C and Cdc2/cyclin B kinase-proteins that are crucial for the G2/M transition. We show that BRCA1 regulates the expression of both Wee1 kinase, an inhibitor of Cdc2/cyclin B kinase, and the 14-3-3 family of proteins that sequesters phosphorylated Cdc25C and Cdc2/cyclin B kinase in the cytoplasm. We conclude that BRCA1 regulates key effectors that control the G2/M checkpoint and is therefore involved in regulating the onset of mitosis.     

Drumming behavior and life history notes of a high-altitude Colorado population of the stonefly Isoperla petersoni Needham

Late instar nymphs and adults of a Colorado Hudsonian zone population of Isoperla petersoni Needham and Christenson were studied during the summer and early fall months of 1998, when stream temperature ranged from 3.3° C to 8.9° C. Early and middle instar nymphs were absent from July to October, and nymphs attained maximum size in mid-August during the 2nd week of adult field presence, suggesting a univoltine-slow life cycle. Nymphs were carnivorous and fed primarily on chironomid larvae. Adults were present from August to mid-October, with peak numbers of adult males and females occurring in mid-September and late September, respectively. Fecundity of field-collected females averaged 94.1 ± 45.15 eggs per female in September ( N = 81) and decreased to 85.2 ± 57.6 in October ( N = 12). Drumming duets were 2-way (male-female), and female answers followed male calls (nonoverlapped) or began before completion of the male call (overlapped). Male calls averaged 11.1 ± 2.09 beats and female answers averaged 6.2 ± 2.99, with mean intervals of 118 and 58 ms, respectively. The average number of female answer beats increased from 5.3 ± 2.56 when duets were nonoverlapped, to 6.6 ± 3.08 when overlapped.     

A New Species of Asclepias (Asclepiadaceae) from Northwestern New Mexico

Asclepias sanjuanensis Heil, Porter, & Welsh, a new species from the pinyon-juniper woodlands of the San Juan River Valley, San Juan County, New Mexico, is described and illustratred. The species appears to be local and rare. Similar to A. ruthiae Maguire, it is distinguished by the greater number of flowers per inflorescence, the larger number of stems, and the pubescence characters.     

Survival and sprouting responses of Chihuahua pine after the Rodeo-Chediski fire on the Mogollon Rim, Arizona

Chihuahua pines ( Pinus leiophylla Schiede and Deppe var. chihuahuana Engelmann) were surveyed on 11 study plots on the Mogollon Rim in east central Arizona to compare characteristics of trees that sprouted from the base or root collar after the Rodeo-Chediski fire with those of trees that did not sprout. The differences in trees killed and top-killed by the fire versus those that survived were also assessed. Trees that sprouted were significantly smaller in height and diameter at breast height; they also experienced lower fire intensities than trees that did not sprout. Smaller trees had higher incidences of mortality than larger trees. These results indicate that, even though Chihuahua pine has fire resiliency, sprouting rates after fire are related to size of trees, age of trees, and burn intensity. Since Chihuahua pine is a rare species in the area studied, its ability to recover from and tolerate fire could prove advantageous for sustainability.     

Additions to knowledge of Paleocene mammals from the North Horn Formation, central Utah

The distinctive but inadequately known Paleocene faunas of central Utah are significant in that they sample a time interval not well represented by sequences in other areas. New materials from the Wagon Road (late Puercan) and Dragon (early Torrejonian) local faunas, North Horn Formation, provide additional information on the composition of the assemblages and systematics of included mammal taxa. The proteutherian ? Propalaeosinopa is recorded for the first time, from the Wagon Road fauna, indicating a significant extension for the enigmatic family Pantolestidae, otherwise first known from the Torrejonian. Associated premolars of Aphronorus simpsoni , a pentacodontid proteutherian from the Dragon fauna, indicated that the species is more distinct from its Torrejonian congener, A. fraudator , than previously suspected. New materials of Desmatoclaenus hermaeus uphold the synonymy of this species with D. paracreodus and permit more adequate definition of the genus with respect to the arctocyonid Loxolophus and the phenacodontid Tetraclaenodon ; because Desmatoclaenus appears to share derived morphology with Loxolophus , we refer it to the basal condylarth family Arctocyonidae. The periptychid condylarth Haploconus , represented in the Wagon Road fauna by the geologically oldest described species of the genus, H. elachistsus , is shown to be distinctive in the configuration of lower molars and premolars; H. elachistus appears to be more primitive than species known from the Torrejonian of New Mexico. Some features of Haploconus are suggestive of the Conacodontinae, a distinctive clade of diminutive periptychids.     

Effects of melezitose and stachyose on adult longevity and virus persistence in Culicoides sonorensis (Diptera: Ceratopogonidae)

A wide variety of blood-feeding Diptera feed on extrafloral sugar sources such as homopteran honeydew. The significance of these sugar sources to insect survival and disease transmission is poorly known. Culicoides sonorensis, a biting midge, can survive on plant sugars but might also feed on homopteran honeydew. The survival of C. sonorensis fed 10% melezitose or 10% stachyose was compared to that of C. sonorensis fed 10% sucrose. A significantly greater number of C. sonorensis survived longer when fed melezitose than when fed either stachyose or sucrose. The effect of sugar meals on vector competence was measured using bluetongue and epizootic hemorrhagic disease viruses. There was no significant difference in viral persistence. However, if C. sonorensis feeds on homopteran honeydew in the wild, a larger number of midges could survive to transmit orbiviruses.     

Gap analysis of the vegetation of the Intermountain Semi-Desert ecoregion

A conservation gap analysis was conducted for the Intermountain Semi-Desert ecoregion to assess the representation of land-cover types within areas managed primarily for biodiversity objectives. Mapped distributions of plant communities were summarized by land-management status categories. The total amount of land permanently protected in the ecoregion is < 4%, and most types that are characteristic of the region have < 10%. Of 48 land-cover types, 20 were found to be particularly vulnerable to potential loss or degradation because of low level of representation in biodiversity management areas and the impact of expected land-use activities. Gap analysis data and findings will be useful in providing a regional perspective in project impact assessment and future conservation planning within this ecoregion.     

Roosting behavior of the Mexican free-tailed bat ( Tadarida brasiliensis ) in a highway overpass

A colony of Mexican free-tailed bats ( Tadarida brasiliensis ) roosting in an interstate highway overpass in Belton, Bell County, Texas, was studied weekly from 28 June to 21 November 1996 (except for the week of 4 July). We examined 2 aspects of roosting behavior: site-specific fidelity to locations within the roost and gender-related segregation within the roost. Colony estimates based on guano production showed a marked decrease in the number of bats from 19 to 26 July; many of these departing bats were adult females. No female bats sampled after this interval were pregnant. Male bats outnumbered females on nearly all sampling occasions. Throughout the study, one section of the roost was dominated by males, ranging from 83% to 100% of total bats. The majority of bats recaptured at least once were faithful to specific locations within the roost, and more than 70% of bats recaptured multiple times were faithful to specific roost locations.