Abstract:
Haptoglobin (Hp) and serum amyloid A (SAA) are two vital proteins involved in inflammatory reactions
and are classified as acute-phase proteins. They are released from hepatocytes under inflammatory
conditions to protect healthy cells from being damaged by pathogens or from self-destructive
mechanisms. In this study, a previously constructed black rockfish (Sebastes schlegeli) cDNA library
was used to identify the full-length cDNA sequences of Hp and SAA homologs (RfHp and RfSAA,
respectively) and characterize them at the molecular level. As expected, in silico analysis of these
homologs showed the typical domain architectures of their known counterparts. Open reading frames of
RfHp and RfSAA consisted of 942-bp and 313-bp DNA sequences, respectively. The derived polypeptide
sequence of RfHp was composed of 313 amino acids (aa) with a predicted molecular weight of 34 kD,
whereas RfSAA had a 121-amino acid sequence with a molecular weight of 13 kD. Phylogenetic analysis
as well as pairwise sequence alignment results showed that RfHp was more closely related to
Oreochromis mossambicus from an evolutionary perspective while RfSAA was closely related to the
Epinephelus coioides ortholog. Although both genes were expressed ubiquitously in the tissues analyzed,
they were particularly expressed in liver tissue, suggesting their origin in hepatocytes. Quantitative
real-time PCR analysis indicated that both RfHp and RfSAA were significantly up-regulated by both
bacterial and viral stimulation in liver tissue, affirming their putative importance in the acute phase of
first-line host immune defenses
