Biomedical subjects

W M Fan

Publications and source records attributed to W M Fan.

4 recordsLinked to original sources

PubMed1991

Cloning of a mu-class glutathione S-transferase complementary DNA and characterization of its glucocorticoid inducibility in a smooth muscle tumor cell line.

A cDNA (designated hGSTYBX) encompassing the complete coding sequence of a hamster mu-class glutathione S-transferase (GST) subunit was cloned from a lambda ZAP library constructed with mRNA isolated from triamcinolone acetonide-treated smooth muscle tumor cells (DDT1 MF-2). Analysis of its nucleotide and deduced amino acid sequences demonstrated highest homology to the rat mu-class GST YB2 subunit. In proliferating subconfluent cells, in which constitutive expression of hGSTYBX mRNA was undetectable, glucocorticoid treatment induced hGSTYBX expression after a time lag of 3 h, and maximal induction occurred at 10 h. Nuclear run-on analysis showed that glucocorticoid induction resulted at least in part from an increased rate of transcription. Simultaneous treatment with glucocorticoid and cycloheximide prevented glucocorticoid induction, but had little effect on basal expression in confluent cells. In contrast, cycloheximide treatment 3 h after glucocorticoid treatment resulted in nearly full induction. These results taken together suggest that hGSTYBX induction may be a secondary glucocorticoid response.

Amino Acid Sequence↗

PubMed1990

Revertants of a mutant of vesicular stomatitis virus which has an aberrant polyadenylation activity and a temperature-sensitive transcriptase.

tsG16(l), a temperature-sensitive mutant of vesicular stomatitis virus, in vitro has at least three phenotypic differences from its parental wild-type (wt) virus due to mutation of the L gene. It was not known whether (i) the temperature-sensitivity of the transcriptase, (ii) the aberrant polyadenylation phenotype, and (iii) the extent of increased polyadenylation in response to S-adenosylhomocysteine (SAH) were associated with a single mutation. Spontaneous partial revertants were selected from tsG16(I) on the basis of the ability to form plaques at 34.7 degrees (35G16 revertants) or from 35G16 revertants on the basis of the ability to form plaques at 37 degrees (37G16 revertants). All six 35G16 revertants had fully (five) or partially (one) recovered the wt polyadenylation phenotype and the former five had also fully recovered the wt polyadenylation response to SAH. This suggested that a single mutation in tsG16(I) was probably associated with both of these phenotypes and also probably conferred the inability to grow at 34.7 degrees. None of the 35G16 revertants regained the wt phenotype for thermosensitivity of the transcriptase, although both of the 37G16 revertants did. This suggested that in vitro temperature-sensitivity of transcription by tsG16(I) might be due to a mutation different than the one affecting polyadenylation in the absence or presence of SAH.

Adenosine Monophosphate↗

PubMed1990

Evolution of the class II major histocompatibility complex alleles in higher primates.

We have shown that chimpanzees and gorillas have DRB alleles very similar to those of humans. The existence of similar DRB alleles in the different species of higher primates cannot be accounted for by convergent evolution of unrelated alleles that arose independently after the speciation. We therefore conclude that ancestral DRB alleles, that had existed before the speciation, were transmitted to the ancestors of humans, chimpanzees, and gorillas. This conclusion indicates that the diversification of MHC alleles does not start at the inception of a species, but rather proceeds beyond the lifespan of a species. A high degree of sequence similarity found between certain human and non-human primate DRB alleles shows that MHC alleles do not diversify rapidly. The bulk of the contemporary DRB polymorphism seems to have been generated by accumulation of random point mutations during long evolutionary periods preceding the divergence of humans, chimpanzees, and gorillas.

Alleles↗

PubMed1989

Shared class II MHC polymorphisms between humans and chimpanzees.

To gain an insight into the evolution of the major histocompatibility complex alleles, three DRB and one DRA genes were isolated from chimpanzee cDNA libraries. The nucleotide sequences of the chimpanzee DRB (ChLA-DRB) genes were then compared with those of the available HLA-DRB alleles by constructing unrooted phylogenetic trees. All three ChLA-DRB genes were found to be more closely related to certain HLA-DRB alleles than unrelated HLA-DRB alleles are to each other. Since available evidence does not support the convergent evolution of MHC alleles, this result is consistent with the idea that closely related ChLA-DRB and HLA-DRB alleles are derived from common ancestral alleles, the existence of which predates the divergence of human and chimpanzee lineages. The predicted amino acid sequences of mature ChLA-DRA and HLA-DRA molecules differ by only one amino acid.

Amino Acid Sequence↗