Submitted to: Gene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2005
Publication Date: 2/24/2006
Citation: MacLea, K.S., Cheng, H.H. 2006. Cloning and expression of deoxyribonuclease II from chicken. Gene. 373:44-51. Available: http://www.sciencedirect.com. Interpretive Summary: DNase II, a lysosomal and secreted endonuclease with an acidic pH optimum, has been shown to be important in DNA fragmentation and degradation following cell death in normal mammalian development. Despite extensive biochemical characterization and its isolation from organisms as varied as nematodes and primates, no identification, expression, or activity, of this enzyme has been reported in an avian species. In this paper, we have cloned and expressed the first chicken DNase II, which demonstrates very similar expression, structure, and function to that seen in mammalian systems. Through comparison with other avian homologous sequences and with known gene structure in other organisms, we have determined that chicken DNase II is properly designated a member of the DNase II beta subfamily. Though it remains to be seen if a DNase II alpha homolog will be identified in the chicken, initial data strongly suggests that chicken DNase II may be the only homolog present in the chicken and therefore may represent the single-copy ancestral form of the enzyme before the evolutionary split between birds and mammals. This result provides valuable information to scientists on the evolution of avian species. Furthermore, it demonstrates the utility of the genome sequence and related databases.
Technical Abstract: Acid endonucleases of the deoxyribonuclease II (DNase II, EC 184.108.40.206) family have been implicated in the degradation of DNA from apoptotic cell corpses formed in the process of normal mammalian development. However, to date no homologs of these important enzymes have been identified in any avian species. Here we report the cloning and expression of DNase II from the chicken, Gallus gallus. When expressed, the 363 amino acid glycoprotein is observed to be approximately 45 kDa in size and to exhibit DNA hydrolytic activity at pH 5 consistent with DNase II in other species. Furthermore, chicken DNase II sequence is compared with an identified partial sequence from the zebra finch, Taeniopygia guttata, as well as the previously identified homologs found in the fowlpox and canarypox viruses and the previously cloned mammalian DNases II. Through analysis of its amino acid sequence, comparative gene structure, and conserved synteny, chicken DNase II appears to represent a member of the DNase II beta subfamily and the apparent lack of a DNase II alpha homolog in the chicken has important evolutionary implications for the study of this gene family.