Eliminated sequences with different copy numbers clustered in the micronuclear genome of Tetrahymena thermophila

Summary As the ciliated protozoan Tetrahymena thermophila develops a new macronucleus (MAC) from products of its micronucleus (MIC), several repetitive sequences are eliminated from the MAC genome. Four MIC DNA clones containing repetitive sequences that are eliminated from the MAC were obtained. One clone contains a representative from each of three families of eliminated sequences. One, present in 200–300 copies in the MIC, is almost completely eliminated from the MAC. A second, present in approximately 50 copies in the MIC, is scattered throughout the genome, although up to half of the family members examined could be localized to chromosome 2. Approximately one tenth of the members of this less repetitive family persist in the MAC while the rest are eliminated. The third type of eliminated sequence has three to four members, all of which are eliminated from the MAC. Three of the members are located on three of the five MIC chromosomes, and one could not be mapped. This sequence is clustered with the other two families of sequences in at least three of the four sites. All three types of eliminated sequences are found in similar arrangements in the MIC of several different inbred strains of T. thermophila.     

Prostatic 25-hydroxyvitamin D-1alpha-hydroxylase and its implication in prostate cancer

Evidence suggests that vitamin D may have a protective role for prostate cancer. 1alpha,25-Dihydroxyvitamin D [1alpha,25(OH)(2)D] inhibits growth and induces differentiation of prostate cells. 25-Hydroxyvitamin D-1alpha-hydroxylase [1alpha-OHase], the enzyme that is responsible for the synthesis of 1alpha,25(OH)(2)D, is expressed in cultured prostate cells. We observed a marked decrease in 1alpha-OHase activity in prostate cancer cells, suggesting some defect of the 1alpha-OHase in these cells. To investigate whether the defect was due to dysregulation of the enzyme at the promoter level, a series of deletion constructs of the promoter was synthesized and incorporated upstream into the luciferase reporter gene. Two regions were identified with high basal activity in transfected normal prostate cell line (PZHPV-7), -1100 bp (AN2), and -394 bp (AN5) upstream of ATG start site of the 1alpha-OHase gene. When the reporter gene with either AN2 or AN5 was transfected into prostate cancer cell lines, we observed a lower basal promoter activity in PC-3 cells and DU145 cells than that found in PZHPV-7 cells for both constructs, and a loss of promoter activity in LNCaP cells. Thus, the results suggest that the defect in enzyme activity may result from the decreased promoter activity in prostate cancer cells.     

Recombinant murine steel factor stimulates in vitro production of granulocyte-macrophage progenitor cells.

The ability of murine Steel factor to promote the in vitro production of granulocyte-macrophage progenitor cells (CFU-GM) was examined in short-term liquid cultures. Bone marrow from C57BL/6J or Sl/Sld mice was placed in culture for seven days with either Steel factor alone or in the presence of IL-3. CFU-GM responsive to GM-CSF, IL-3, and CSF-1 were measured in the input population and again after 3 or 7 days in culture. Steel factor alone increased the number of all CFU-GM types as early as 3 days after culture initiation, with further increases at day 7. This effect was potentiated by the addition of IL-3. Production of CFU-GM by C57BL/6J or Sl/Sld marrow was comparable except for enhanced production of CSF-1 responsive progenitors by Sl/Sld marrow. A recombinant Sld protein was also shown to be equivalent to the wild-type protein in its capacity to promote CFU-GM production from normal bone marrow.     

Cultural traits as units of analysis

Cultural traits have long been used in anthropology as units of transmission that ostensibly reflect behavioural characteristics of the individuals or groups exhibiting the traits. After they are transmitted, cultural traits serve as units of replication in that they can be modified as part of an individual's cultural repertoire through processes such as recombination, loss or partial alteration within an individual's mind. Cultural traits are analogous to genes in that organisms replicate them, but they are also replicators in their own right. No one has ever seen a unit of transmission, either behavioural or genetic, although we can observe the effects of transmission. Fortunately, such units are manifest in artefacts, features and other components of the archaeological record, and they serve as proxies for studying the transmission (and modification) of cultural traits, provided there is analytical clarity over how to define and measure the units that underlie this inheritance process.     

Macronuclear persistence of sequences normally eliminated during development in Tetrahymena thermophila

During conjugation in the ciliated protozoan, Tetrahymena thermophila, a somatic MAC-ronucleus develops from the germinal MICronucleus. Ten to 20 percent of the MIC genome is eliminated during this process. Three repetitive families have been identified which have different levels of repetition in the MIC and are eliminated to different degrees in the MAC. Some members of two of these families persist in the MAC. In this study, we have looked at these persistent sequences in the MAC of cell lines from a variety of sources including several inbed strains, two sets of caryonides, caryonidal subclones, and vegetatively aged cell clones. The results suggest that the sequences that remain in the MAC have a genetic predisposition to persist. However, epigenetic variations occur as the MAC develops so that only some of the persistent sequences are actually observed in a particular MAC. Polymorphisms may be generated if alternative processing of a single MIC segment occurs. These polymorphisms can later be resolved by phenotypic assortment during vegetative growth. These facultatively persistent sequences appear to differ from sequences previously described in this organism.