Molecular Systematics of the Order Crocodilia

Analyses of proteins, lipids and nucleic acids have been extremelyuseful for assessing the level of molecular divergence in theCrocodilia and for inferring the relationships of crocodiliansto each other and to other vertebrates. A large body of traditional(morphological and paleontological), as well as recent non-traditional(cytogenetic and molecular) evidence concurs that birds arethe closest living sister group to the Crocodilia. Relationshipswithin the order have been much more difficult to resolve usingtraditional analyses due to the problems of convergence/parallelismand general morphological conservatism. Studies of protein divergence,while in agreement with traditional interpretations of affinitiesbetween the alligators and caimans, suggest that the true andfalse gharials are more closely related to each other than toother crocodilians and that the true crocodiles are all veryclose relatives that may have diverged recently. Preliminaryanalyses from an ongoing study of restriction endonuclease analysisof crocodilian mitochondrial and ribosomal DNAs corroborateboth of these observations, suggesting that the molecular approachwill be very valuable for resolving crocodilian phylogeny.     

ISOLATION AND EXPRESSION OF THE INTERLEUKIN-2 GENE FROM THE KILLER WHALE, ORCINUS ORCA

Complementary DNA encoding interleukin-2 (IL-2) was isolated, cloned, and sequenced from the killer whale, Orcinus orca . The sequence of the killer whale IL-2 coding region consists of 455 nucleotides which translate into a polypeptide containing 151 amino acids. Killer whale IL-2 displays 88%, 88%, 87%, 87%, 85%, 84%, 80%, and 71% nucleotide sequence homology and 76%, 76%, 76%, 73%, 68%, 73%, 64%, and 56% amino acid homology with the cow, sheep, pig, red deer, horse, human, manatee, and mouse, respectively. High levels of killer whale recombinant IL-2 were generated by transiently transfecting killer whale IL-2/pCMV Blue plasmid DNA into cultured monkey kidney cells (Cos-1). Generation of this recombinant IL-2 will allow the development of assays useful for assessing IL-2 levels in the serum and from isolated lymphocytes of killer whales and possibly other species of cetaceans. A major contribution and significance of the in vitro expression of killer whale IL-2 exists in its potential to be used as a therapeutic agent.     

The Target of the NSD Family of Histone Lysine Methyltransferases Depends on the Nature of the Substrate

The NSD (nuclear receptor SET domain-containing) family of histone lysine methyltransferases is a critical participant in chromatin integrity as evidenced by the number of human diseases associated with the aberrant expression of its family members. Yet, the specific targets of these enzymes are not clear, with marked discrepancies being reported in the literature. We demonstrate that NSD2 can exhibit disparate target preferences based on the nature of the substrate provided. The NSD2 complex purified from human cells and recombinant NSD2 both exhibit specific targeting of histone H3 lysine 36 (H3K36) when provided with nucleosome substrates, but histone H4 lysine 44 is the primary target in the case of octamer substrates, irrespective of the histones being native or recombinant. This disparity is negated when NSD2 is presented with octamer targets in conjunction with short single- or double-stranded DNA. Although the octamers cannot form nucleosomes, the target is nonetheless nucleosome-specific as is the product, dimethylated H3K36. This study clarifies in part the previous discrepancies reported with respect to NSD targets. We propose that DNA acts as an allosteric effector of NSD2 such that H3K36 becomes the preferred target.     

The Lumpy Breast

“Topics in Primary Care Medicine” presents articles on common diagnostic or therapeutic problems encountered in primary care practice. Physicians interested in contributing to the series are encouraged to contact the series'' editors.     

Isolation of Serratia marcescens on Deoxyribonuclease-Toluidine Blue-Cephalothin Agar

Serratia marcescens was isolated on a new medium-commercial deoxyribonuclease agar with the addition of cephalothin (1,000 mug/ml) and Toluidine Blue (1,000 mug/ml). It was detected in water samples even though it comprised only 0.1 to 0.0001% of the total bacterial population.