Biomedical subjects

Yikang S Rong

Publications and source records attributed to Yikang S Rong.

5 recordsLinked to original sources

PubMed2004

Drosophila melanogaster MNK/Chk2 and p53 regulate multiple DNA repair and apoptotic pathways following DNA damage.

We have used genetic and microarray analysis to determine how ionizing radiation (IR) induces p53-dependent transcription and apoptosis in Drosophila melanogaster. IR induces MNK/Chk2-dependent phosphorylation of p53 without changing p53 protein levels, indicating that p53 activity can be regulated without an Mdm2-like activity. In a genome-wide analysis of IR-induced transcription in wild-type and mutant embryos, all IR-induced increases in transcript levels required both p53 and the Drosophila Chk2 homolog MNK. Proapoptotic targets of p53 include hid, reaper, sickle, and the tumor necrosis factor family member EIGER: Overexpression of Eiger is sufficient to induce apoptosis, but mutations in Eiger do not block IR-induced apoptosis. Animals heterozygous for deletions that span the reaper, sickle, and hid genes exhibited reduced IR-dependent apoptosis, indicating that this gene complex is haploinsufficient for induction of apoptosis. Among the genes in this region, hid plays a central, dosage-sensitive role in IR-induced apoptosis. p53 and MNK/Chk2 also regulate DNA repair genes, including two components of the nonhomologous end-joining repair pathway, Ku70 and Ku80. Our results indicate that MNK/Chk2-dependent modification of Drosophila p53 activates a global transcriptional response to DNA damage that induces error-prone DNA repair as well as intrinsic and extrinsic apoptosis pathways.

Animals↗

PubMed2003

Targeting multi-cellular organisms.

For many years, biologists' efforts in achieving gene targeting by homologous recombination in multicellular organisms have been hampered by the difficulty in culturing pluripotent stem cells. Recent advances have eliminated this requirement for several animal species. For large mammals, cloning by nuclear transfer has led to the first knockout sheep and pigs. For Drosophila, whole organism gene targeting was accomplished by a method for the generation of linear DNA in vivo.

Animals↗

PubMed2003

The homologous chromosome is an effective template for the repair of mitotic DNA double-strand breaks in Drosophila.

In recombinational DNA double-strand break repair a homologous template for gene conversion may be located at several different genomic positions: on the homologous chromosome in diploid organisms, on the sister chromatid after DNA replication, or at an ectopic position. The use of the homologous chromosome in mitotic gene conversion is thought to be limited in the yeast Saccharomyces cerevisiae and mammalian cells. In contrast, by studying the repair of double-strand breaks generated by the I-SceI rare-cutting endonuclease, we find that the homologous chromosome is frequently used in Drosophila melanogaster, which we suggest is attributable to somatic pairing of homologous chromosomes in mitotic cells of Drosophila. We also find that Drosophila mitotic cells of the germ line, like yeast, employ the homologous recombinational repair pathway more often than imperfect nonhomologous end joining.

Animals↗

PubMed2002

Gene targeting by homologous recombination: a powerful addition to the genetic arsenal for Drosophila geneticists.

A series of recent publications have firmly established the notion that Drosophila researchers now have a general method to subject genes for targeted modification by homologous recombination (HR) [Science 288 (2000) 2013; Genetics 157 (3) (2001) 1307; Genes Dev. 16 (12) (2002) 1568; Genetics 161 (2002) 1125-1136]. This method allows one to knockout essentially any gene starting with the DNA sequence of the gene. It has greatly enhanced studies of gene function as demonstrated by over 20 years of gene targeting practice in yeast and mouse. Here, I discuss the basic targeting methodology for eukaryotic organisms. I compare the Drosophila method with the traditional targeting scheme in yeast and mouse mainly to show that the targeting mechanism as well as many aspects of the experimental design remain unchanged, and that the Drosophila scheme differs only in the way in which the donor molecule for targeting is generated. I propose that the Drosophila method can be readily adapted in other organisms without culturable stem cells, since the mechanism for in vivo donor generation in Drosophila is likely to be functional in a variety of different organisms.

Animals↗

PubMed2002

Targeted mutagenesis by homologous recombination in D. melanogaster.

We used a recently developed method to produce mutant alleles of five endogenous Drosophila genes, including the homolog of the p53 tumor suppressor. Transgenic expression of the FLP site-specific recombinase and the I-SceI endonuclease generates extrachromosomal linear DNA molecules in vivo. These molecules undergo homologous recombination with the corresponding chromosomal locus to generate targeted alterations of the host genome. The results address several questions about the general utility of this technique. We show that genes not near telomeres can be efficiently targeted; that no knowledge of the mutant phenotype is needed for targeting; and that insertional mutations and allelic substitutions can be easily produced.

Alleles↗