Biomedical subjects

K M Zhou

Publications and source records attributed to K M Zhou.

4 recordsLinked to original sources

PubMed1990

Transcriptional activator LEU3 of yeast. Mapping of the transcriptional activation function and significance of activation domain tryptophans.

The LEU3 protein of yeast activates a number of genes in the branched chained amino acid pathways. Native LEU3 is modulated by alpha-isopropylmalate, an intermediate in leucine biosynthesis. alpha-Isopropylmalate is needed for transcriptional activation, but not for DNA binding. We show here that the transcriptional activation function of LEU3 resides within the C-terminal 32 amino acids. An adjacent stretch of 81 residues is dispensable and apparently forms a connecting link between the activation domain and a large central region previously identified as important for modulation. The newly defined activation domain contains a cluster of three tryptophan residues, each of which was changed to alanine by site-directed mutagenesis. Surprisingly, all three Trp----Ala mutations affect modulation. One of them, Trp-864----Ala, creates a LEU3 molecule that is largely unmodulated and also is a better transcriptional activator than is wild type LEU3 ("hyperactivator"). The other two mutations (Trp-861----Ala and Trp-870----Ala) change the modulation ratio but have no effect on the maximal activation efficiency of the activator. We propose that the activation domain of LEU3 is kept silent by association with the central region of the protein and that an alpha-isopropylmalate-induced conformational change in the central region releases and thus activates the activation domain.

Base Sequence↗

PubMed1990

Yeast regulatory protein LEU3: a structure-function analysis.

Eleven mutations resulting in partially deleted or truncated LEU3 protein were generated by linker insertion or other modifications at restriction sites, deletion of restriction fragments, or oligonucleotide-directed mutagenesis. Functional studies of these mutants showed the following: (i) A specific DNA binding region is contained within the 173 N-terminal residues, but other regions of the protein are required for optimal binding. (ii) Activation of LEU2 expression depends on the C-terminal 113 residues of the LEU3 protein. (iii) Deletion of part or all of a central section of LEU3 eliminates the ability of the LEU3 protein to respond to the co-activator alpha-isopropylmalate, i.e. creates an unmodulated activator. (iv) Overproduction of unmodulated activator slows down cell growth. (v) Specific deletion of two short acidic regions, including one with net charge - 19, has only minor effects on activation and modulation.

Amino Acid Sequence↗

PubMed1988

[Establishment and characteristics of a human synovial sarcoma cell line].

A human synovial sarcoma cell line (HSS-84), from a painful mass excised locally near the left sternoclavicular joint, was established and has been continuously propagated in vitro for more than one year through 54 passages till the end of 1985. Doubling time was 65 hr. The index of mitosis was 28.8%. The chromosome number for most of the cells was hypertriploid. The cells, stored in liquid nitrogen, had a good revival. Cytologically, some cells, showing elongated, spindle, stellate or spidery shape with prominent processes, were arranged in loose or bundled pattern, similar to sarcoma cells; some cells showed ovoid and polygonal in mosaic arrangement, similar to epithelioid cells. Both features indicated biphasic differentiation of the cells. By electron microscopy, the cells consisted of light and dark cells with microvilli and obvious abnormality. Histopathologically, the tumor, from which HSS-84 originated, was a biphasic differentiation synovial sarcoma. It was composed of malignant spindle interstitial cells and malignant epithelioid cells lining the clefts or spaces. The latter was similar to cultured cells by electron microscopy. HSS-84 was identical with the donor. HSS-84 establishment will be useful for research on diagnosis, therapy, origin and biphasic differentiation of the synovial sarcoma.

Animals↗

PubMed1987

[Establishment of a human lung alveolar cancer cell strain and its characteristics].

A human lung alveolar cancer cell strain (HAC-84), isolated from lung adenocarcinoma cell line in Gejiu (GLC-82) by colony selecting method, has been continuously propagated in vitro for more than 2 years through 164 passages till May 1 st 1986. HAC has the typical malignant characteristics as GLC. There are plenty of phospholipid and osmiophilic multilamellar bodies in the cytoplasm of all cells and the membrane-like material in most of the nuclei, which differentiate HAC from GLC and the other types of lung cancers. The cytoplasmic inclusions are the same as those found in type II alveolar epithelial cells of the lung. So, HAC, originated from the type II alveolar cells, is identified as human lung alveolar cancer cell strain. It is significant in the research of the properties and origin of the alveolar cancer, the action and formation of the alveolar surfactants.

Adenocarcinoma↗