Identification and sequencing of cDNA clones for the rodent negative acute‐phase protein α₁‐inhibitor 3

Abstract

Rat α1‐inhibitor 3 clones were isolated by immunological screening of a λ gt11 cDNA library prepared from rat liver poly(A)‐rich RNA. The recombinant cDNA clones were identified by the absence of their immunoprecipitable products following hybrid‐arrested in vitro translation. The size of the cognate poly(A)‐rich RNA was estimated to be roughly 5000 residues. Approximately 16 h after induction of inflammation the amount of α1‐inhibitor 3 poly(A)‐rich RNA decreases as shown by dot‐blot hybridization and Northern analyses. The response of this negative acute‐phase plasma protein to inflammation may therefore be considered to be at the pretranslational level. The characterized DNA constitutes an open reading frame of 225 amino acids followed by a canonical eucaryotic polyadenylation signal and a poly(A) tail. Sequence microheterogeneity, particularly in the 3′‐flanking region was observed. An amino acid homology of 70% for α1‐inhibitor 3 with human and rodent α2‐macroglobulin emphasizes the evolutionary relationship of the macroglobulins.

Differential regulation of the two mRNA species of the rodent negative acute phase protein α1‐inhibitor 3

“…1), The mRNA species from which the clones MT, M57, A22, B4, B12 and B21 have been derived has been named ~t-I3 variant I and the other which gave rise to pI3cDNA6 [6], M2, M34, M35, M22, BI6 and B25 has been designated =~-I3 variant II. The entire ect-13 variant I eDNA sequence is shown in Fig.…”

“…We find the N-terminus of mature o~t-I3 [3] is encoded by nt 124 to 169 of the eDNA sequence ( and II, Shown below each bar are the relative locations of their constituent cDNA clones, pI3cDNA6 has been described previously [6]. M7, M57, M2, M34, M35, M22 were obtained by screening the c~=.13 specific library and sequenced over both strands in their entirety: The hatched region of N122 represents a clotnng artefact.…”

“…I1. The ~3 bp d~lCtled in t~-13 eDNA variant II and tile three r~t deleted in w=.13 eDNA variant [ are indicated by dots, homology found in the two en-13 spccies also extends to a~-macroglobulins of human [22,23] and rat [6,9]. It could be shown that the receptors are responsible for removing proteinase complexed with either c~t-13 [5] or c~-macroglobulin [13] from the serum.…”

“…To determine whether or not the reduction in the amount of c~t-I3 mRNA which we documented previously [6] is due to a switching-off of one or other or both aa-13 mRNA species specific riboprobes were hybridized to filter-bound total RNA from the livers of normal and turpentine-treated rats. As seen in Fig.…”

“…To study the regulation of on-13 at the molecular level we isolated corresponding eDNA clones for this proteinase inhibitor [6]. Sequencing revealed a significant number of nucleotide (nt) exchanges between the clones suggesting that there are at least two transcribed 0~I3 genes.…”