No abstract

The centromere is essential for faithful chromosome segregation by providing the site for kinetochore assembly. Although the role of the centromere is conserved throughout evolution, the DNA sequences associated with centromere regions are highly divergent among species and it remains to be determined how centromere DNA directs kinetochore formation. Despite the active use of chicken DT40 cells in studies of chromosome segregation, the sequence of the chicken centromere was unclear. Here, we performed a comprehensive analysis of chicken centromere DNA which revealed unique features of chicken centromeres compared with previously studied vertebrates. Centromere DNA sequences from the chicken macrochromosomes, with the exception of chromosome 5, contain chromosome-specific homogenous tandem repetitive arrays that span several hundred kilobases. In contrast, the centromeres of chromosomes 5, 27, and Z do not contain tandem repetitive sequences and span non-tandem-repetitive sequences of only ;30 kb. To test the function of these centromere sequences, we conditionally removed the centromere from the Z chromosome using genetic engineering and have shown that that the non-tandem-repeat sequence of chromosome Z is a functional centromere.

Fifty-five triterpenoids consisting of 19 tetracyclic, 32 pentacyclic, and 4 incompletely cyclized triterpenoids, and 2 sterols, mostly isolated from various plant and fungal materials, were examined for their inhibitory effects on a purified human immunodeficiency virus type 1 (HIV-1) reverse transcriptase. Twenty triterpenoids and one sterol showed inhibitory effects with 50% inhibition concentration (IC50) values less than 5.0 microM. Among these cycloartenol ferulate (IC50 = 2.2 microM), 24-methylenecycloartanol ferulate (1.9 microM), lupenone (2.1 microM), betulin diacetate (1.4 microM), and karounidiol 29-benzoate (2.2 microM) inhibited most effectively. Some of the triterpenoids and sterols may be potential new lead compounds to find still more potent HIV-1 reverse transcriptase inhibitors.

No abstract

No abstract