Search PubMed⌕ Search

Biomedical subjects

D K Watson

Publications and source records attributed to D K Watson.

77 records · Page 5Linked to original sources
PubMed1976

A chromatin-bound proteolytic activity with unique specificity for histone H2A.

A protease associated with purified calf thymus chromatin has been found to act exclusively upon histone H2A, yielding a single new protein species, cH2A. This fragment migrates faster than H2A in acrylamide gel electrophoresis under denaturing conditions. The cH2A was purified and subjected to amino acid analysis and partial sequencing by the use of carboxypeptidase A. These studies demonstrated that cH2A had been derived from the removal of fifteen amino acids from the carboxy-terminal end of the intact H2A molecule, and that valine114 was its new carboxy-terminal residue. This cleavage does not occur under low ionic strength conditions, where H2A is believed to approximate a random coil; rather, it requires high ionic strength conditions similar to those under which the H2A molecule undergoes radical secondary and tertiary structural changes. This dependence upon ionic strength implies that the proteolytic cleavage is conformation- as well as sequence-specific. The H2A-specific protease is of nuclear origin, since isolation of nuclei by methods designed to maximize or minimize cytoplasmic contamination does not affect the level of proteolytic activity associated with purified chromatin. This nuclear protease appears to be tightly associated with the chromatin in vivo, for 0.6 M NaCl will not free it from isolated chromatin. A concentration of 1.2 M NaCl is required to dissociate the protease as well as its substrate from chromatin. The relationship of this enzyme to previously reported chromatin-bound proteases is discussed.

Animals↗
PubMedDate not supplied

Two oncogenes in avian carcinoma virus MH2: myc and mht.

The 5.2-kilobase (kb) RNA genome of avian carcinoma virus MH2 has the genetic structure 5' - delta gag (0.2 kb)-mht (1.2 kb)-myc (1.4 kb)-c(0.4 kb)-poly (A) (0.2 kb)-3'. delta gag is a partial retroviral core protein, mht and myc are cell-derived MH2-specific sequences, and c is the 3'-terminal retroviral vector sequence. the following results were obtained from the complete nucleotide sequences of the mht and myc genes in MH2. (i) delta gag-mht forms a hybrid gene with a contiguous reading frame of 2682 nucleotides that terminates with a stop codon near the 3' end of the mht gene. The 3' 969 nucleotides of mht up to the stop codon are 80% sequence related to the onc-specific raf sequence of murine sarcoma virus 3611 (MSV 3611) (94% homologous at the deduced amino acid level). (ii) The myc coding region in MH2 is preceded by 181 nucleotides derived from the intron immediately upstream from the second exon of the chicken cellular proto-myc gene, followed by an RNA splice acceptor site shared with the proto-myc gene, followed by an RNA splice acceptor site shared with the proto-myc, beyond which it is colinear up to a 3'-termination codon and 40 noncoding nucleotides with the myc sequences of avian retrovirus MC29 and chicken proto-myc. Thus, myc forms, together with a 5' retroviral exon, a second MH2-specific gene. It is concluded that MH2 contains two genes with oncogenic potential, the delta gag-mht gene, which is closely related to the delta gag-raf transforming gene of MSV 3611, and the myc gene, which is related to the transforming gene of MC29. Furthermore, it may be concluded that the cellular proto-onc genes, which on sequence transduction become viral onc genes, are a small group because among the 19 known onc sequences, 5 are shared by different taxonomic groups of viruses of which the mht/raf homology is the closest so far.

Alpharetrovirus↗
PubMedDate not supplied

The avian and mammalian ets genes: molecular characterization, chromosome mapping, and implication in human leukemia.

The mammalian homologs of the ets-region from the transforming gene of avian erythroblastosis virus, E26, consist of two distinct domains located on different chromosomes. Using somatic cell hybrid panels, the mammalian homologs of the 5' v-ets-domain, ets-1, were mapped to chromosome 11 in man, to chromosome 9 in mouse, and to chromosome D1 in cat. The mammalian homologs of the 3'v-ets domain, ets-2, were similarly mapped to human chromosome 21, to mouse chromosome 16, and to feline chromosome C2. We conclude that the ets sequence shared by the virus, chicken, and man is likely to contain at least two functionally dissociable domains, identifiable as ets-1 and ets-2. The human ets- locus is transcriptionally active and encodes a single mRNA of 6.8 kb, while the second locus, human ets-2 encodes three mRNAs of 4.7, 3.2 and 2.7 kb. By contrast, the chicken homolog, having a contiguous ets-1 and ets-2 sequence, is primarily expressed in normal chicken cells as a single 7.5 kb mRNA. Because chromosome translocations have been associated with different human hematopoietic malignancies, we have used our human probes to study specific translocations occurring in acute leukemias. The human ets- gene was found to translocate from chromosome 11 to 4 in t(4;11) (q21;23) and the human ets-2 gene was found to translocate from chromosome 21 to 8 in t(8;21) (q22;q22). Significantly, both translocations were associated with an expression of ets genes which differed from that found in normal diploid lymphoid cells.

Acute Disease↗