ABSTRACT
Kaposi's sarcoma-associated herpesvirus (KSHV) LANA is an 1,162-amino-acid protein that tethers terminal repeat (TR) DNA to mitotic chromosomes to mediate episome persistence in dividing cells. C-terminal LANA self-associates to bind TR DNA. LANA contains independent N- and C-terminal chromosome binding regions. N-terminal LANA binds histones H2A/H2B to attach to chromosomes, and this binding is essential for episome persistence. We now investigate the role of C-terminal chromosome binding in LANA function. Alanine substitutions for LANA residues 1068LKK1070 and 1125SHP1127 severely impaired chromosome binding but did not reduce the other C-terminal LANA functions of self-association or DNA binding. The 1068LKK1070 and 1125SHP1127 substitutions did not reduce LANA's inhibition of RB1-induced growth arrest, transactivation of the CDK2 promoter, or C-terminal LANA's inhibition of p53 activation of the BAX promoter. When N-terminal LANA was wild type, the 1068LKK1070 and 1125SHP1127 substitutions also did not reduce LANA chromosome association or episome persistence. However, when N-terminal LANA binding to chromosomes was modestly diminished, the substitutions in 1068LKK1070 and 1125SHP1127 dramatically reduced both LANA chromosome association and episome persistence. These data suggest a model in which N- and C-terminal LANA cooperatively associates with chromosomes to mediate full-length LANA chromosome binding and viral persistence.
Colchicine-induced autotetraploids of Triticum speltoides, T. longissimum, T. sharonense, T. bicorne, T. uniaristatum, T. monococcum, and T. tauschii were all morphologically similar to but larger than their diploid forms. Seed set was lower than in the diploids except for the autotetraploid T. speltoides. Meiotic analysis showed fewer quadrivalents and more bivalents than would be expected in all of these autotetraploids. Arm-pair switch, indicated by complex trivalents and quadrivalents, was found and involved 0.1% of total chromosomes in T. umbellulatum, 0.5% in T. longissimum, 0.7% in both T. sharonense and T. tauschii, 6.3% in T. bicorne, and 15.3% in T. uniaristatum.Key words: meiosis, chromosome association, arm-pair switch, chromosome pairing, bivalentization.
Cytological and morphological characteristics of a new species, Pseudoroegneria deweyi K. B. Jensen, from the Karachayevo-Cherkesskaya Avtonomnaya Oblast' Region of Russia are described. This species is cytologically stable, genomically similar to Pseudoroegneria tauri, highly fertile (cross-pollinating), and morphologically unique compared with most other species in the genus. Pseudoroegneria deweyi differs from other closely related species in the number of rachis nodes in the inflorescence. Pseudoroegneria stipifolia (2n = 2x = 14, SS) and Agropyron cristatum (2n = 2x = 14, PP) were used as male parents in crosses with P. deweyi. All three P. deweyi accessions studied were tetraploids (2n = 28) and behaved meiotically as allotetraploids with a mean chromosome association of 0.03 I + 13.30 II + 0.03 III + 0.26 IV per cell. In the hybrid P. deweyi × A. cristatum, average chromosome association was 5.92 I + 4.55 II + 1.83 III + 0.09 IV per cell, while the average chromosome association in P. deweyi × P. stipifolia was 4.98 I + 5.23 II + 1.73 III 0.04 IV per cell. Pseudoroegneria deweyi joins P. tauri as the only other known naturally occurring species with the genomic formula of SSPP. Cluster analysis of 21 morphological characters supports the inclusion of P. deweyi as part of the genus Pseudoroegneria rather than Agropyron. Key words: Agropyron, Pseudoroegneria, chromosome pairing, meiosis, Triticeae, new species.
Role of Kaposi's Sarcoma-Associated Herpesvirus C-Terminal LANA Chromosome Binding in Episome Persistence