Faculty Bibliography

Two mutants containing large deletions in the E4 region of the adenovirus genome H5dl366 (91.9-98.3 map units) and H2dl808 (93.0-97.1 map units) were used to investigate the role of E4 genes in adenovirus DNA synthesis. Infection of KB human epidermoid carcinoma cells with either mutant resulted in production of large concatemers of viral DNA. Only monomer viral genome forms were produced, however, when mutants infected W162 cells, a monkey kidney cell line transformed with and expressing the E4 genes. Diffusible E4 gene products, therefore, complement the E4 mutant phenotype. The viral DNA concatemers produced in dl366- and dl808-infected KB cells did not have any specific orientation of monomer joining: the junctions consisted of head-to-head, head-to-tail, and tail-to-tail joints. The junctions were covalently linked molecules, but molecules were not precisely joined, and restriction enzyme maps revealed a heterogeneous size distribution of junction fragments. A series of mutants that disrupted single E4 open reading frames (ORFs) was also studied: none showed phenotypes similar to that of dl366 or dl808. Mutants containing defects in both ORF3 and ORF6, however, manifested the concatemer phenotype, indicating redundancy in genes preventing concatemer formation. These data suggest that the E4 ORFs 3 and 6 express functions critical for regulation of viral DNA replication and that concatemer intermediates may exist during adenovirus DNA synthesis

An endobronchial lesion with lung abscess in a patient with AIDS was due to Rhodococcus equi. The patient responded to triple chemotherapy

The genome of the protozoan Trypanosoma brucei contains a set of about 100 minichromosomes of about 50 to 150 kb in size. The small size of these chromosomes, their involvement in antigenic variation, and their mitotic stability make them ideal candidates for a structural analysis of protozoan chromosomes and their telomeres. We show that a subset of the minichromosomes is composed predominantly of simple-sequence DNA, with over 90% of the length of the minichromosome consisting of a tandem array of 177-bp repeats, indicating that these molecules have limited protein-coding capacity. Proceeding from the tip of the telomere to a chromosome internal position, a subset of the minichromosomes contained the GGGTTA telomere repeat, a 29-bp telomere-derived repeat, a region containing 74-bp G + C-rich direct repeats separated by approximately 155 bp of A + T-rich DNA that has a bent character, and 50 to 150 kb of the 177-bp repeat. Several of the minichromosome-derived telomeres did not encode protein-coding genes, indicating that the repertoire of telomeric variant cell surface glycoprotein genes is restricted to some telomeres only. The telomere organization in trypanosomes shares striking similarities to the organization of telomeres and subtelomeres in humans, yeasts, and plasmodia. An electron microscopic analysis of the minichromosomes showed that they are linear molecules without abnormal structures in the main body of the chromosome. The structure of replicating molecules indicated that minichromosomes probably have a single bidirectional origin of replication located in the body of the chromosome. We propose a model for the structure of the trypanosome minichromosomes