G. Poznanovic et al., REGIONS OF THE HAPTOGLOBIN 5' FLANKING GENE SEQUENCE SHOW DIFFERENT BINDING AFFINITIES TO NUCLEAR MATRIX PROTEINS DURING THE ACUTE-PHASE RESPONSE, Journal of Biochemistry, 115(3), 1994, pp. 422-428
The effect of the acute phase response on the affinity of binding betw
een nuclear matrix proteins and the rat haptoglobin (Hp) gene region w
as examined. Nuclear matrices isolated from acute phase livers were en
riched with the 5' Hp gene flanking region (-705/+159), but not with t
he spliced, protein-coding sequence. Reassociation experiments with is
olated nuclear protein matrix spheres and end-labeled fragments I (-14
6/+156), II (-146/-541), and III (-541/-705) revealed that the matrix
proteins displayed an increased binding potential during the acute pha
se response for all of the examined regions, this being most pronounce
d for fragment II. BAL 31 digestion of fragment II showed that the seq
uence element that was responsible for the increased association with
nuclear matrix proteins during the acute phase response was a tract of
38 adenine bases. The DNA region established stable associations with
nuclear lamin B (67 kDa, pI 5.7) in the controls, and with lamins A (
69 kDa, pI 7.0), B, isoforms of lamin C (62 kDa, pI 6.55-6.95), and a
55-kDa (pI 5.9) polypeptide during the acute phase response. Sequence
ABC (-165/-56), which overlaps fragments I and II and represents the H
p cis-acting element, did not bind to the non-histone nuclear matrix p
roteins.