The HO gene product of Saccharomyces cerevisiae is a site-specific endonuclease that initiates mating type interconversion. We have determined the nucleotide sequence of a 3,129-base-pair (bp) ...segment containing HO. The segment contains a single long open reading frame encoding a polypeptide of 586 amino acids, which has unusual (unbiased) codon usage and is preceded by 762 bp of upstream region. The predicted HO protein is basic (16% lysine and arginine) and is calculated to have a secondary structure that is 30% helical. The corresponding transcript is initiated approximately 50 nucleotides prior to the presumed initiation codon. Insertion of an Escherichia coli lacZ gene fragment into the putative HO coding segment inactivated HO and formed a hybrid HO-lacZ gene whose beta-galactosidase activity was regulated by the mating type locus in the same manner as HO (repressed by a1-α2). Upstream regions of 1,360 and 762 bp conferred strong repression; 436 bp led to partial constitutivity and 301 bp to full constitutivity. Thus, DNA sequences that confer repression of HO by a1-α2 are at least 250 nucleotides upstream of the transcription start point and are within 436 nucleotides of the HO initiation codon. The progressive loss of repression suggests that both the -762 to -436 and the -436 to -301 intervals contain sites for regulation by a1-α2. The HO gene contains two distinct regions that promote autonomous replication of plasmids in S. cerevisiae. These regions contain sequences that are homologous to the two conserved sequences that are associated with ARS activity.
Hypertonic extracts from human fetuses (10--22 wk of gestation) were used to test the sensitizaton of leukocytes from cancer patients against fetal antigens in a direct, microcapillary tube assay ...system. Leukocytes were simultaneously exposed to a panel of allogeneic tumor extracts and a panel of fetal extracts. Leukocytes from 24 gastric cancer patients, 43 colorectal cancer patients, and 13 lung cancer patients were assayed with extracts obtained from gastric, colorectal, and oat cell carcinomas, respectively, and these extracts were also used with leukocytes from 41 patients bearing tumors of various other organs. Significant migration inhibition by tumor extracts was observed in 81.6% of the tests with gastric cancer, 67.4% of the tests with colorectal cancer, 69.0% of the tests with lung cancer, and 51.2% of the tests with other types of cancer. With fetal extracts, significant migration inhibition occurred in 58.3, 58.7, 59.6, and 54.9% of the tests, respectively. Reactivity against fetal extracts did not depend on the gestation age of the fetuses used for extraction. The conclusion was reached that the leukocytes of most of the cancer patients were sensitized against substances contained in fetal extracts irrespective of the type of tumor of the leukocyte donor. The cross-reactivity pattern suggested that 3-M KCl extracts of whole human fetuses contained a complex mixture of specificities related to the various fetal organs and tissues, which may have represented counterparts to most of the tumor-associated specificities.
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