The activity of a 70 kilodalton I kappa B molecule identical to the carboxyl terminus of the p105 NF-kappa B precursor is modulated by protein kinase A.
The p50 subunit of NF-kappa B is derived from the amino terminus of a 105 kilodalton precursor. The p105 carboxyl terminus, which contains ankyrin-like repeats, a feature of I kappa B molecules, regulates the cytoplasmic retention of p105 and inhibits DNA binding by the precursor. Here, we describe an I kappa B protein identical to the carboxyl-terminal region of p105. Probes spanning the COOH terminus but not the rel homology domain of p105 hybridize to a distinct 2.6-kilobase mRNA expressed in a wide range of murine tissues. The nucleotide sequence of complementary DNA clones for this transcript, in vitro translation, and immune precipitation of metabolically labeled cell lysates establish that it encodes a 70 kilodalton protein that corresponds to the COOH-terminal 607 amino acids of p105. p70 suppresses p65 and p75c-rel mediated transactivation of reporter genes under the control of NF-kappa B elements and in vitro can prevent DNA binding of p50 and p75c-rel homodimers to NF-kappa B sites. The ability of p70 to stably associate with p49 and p65 in vitro, but not inhibit DNA binding by these proteins, suggests that the specific inhibitory properties of this I kappa B may reflect its relative affinity for different rel targets. p70 phosphorylated by protein kinase A fails to inhibit DNA binding by p50 or the c-rel protein, and sequencing of radiolabeled p70 tryptic phosphopeptides establishes that protein kinase A phosphorylates serine residue 576 of p70. This finding suggests that the inhibitory activity of p70 can be regulated by signaling via the adenylate cyclase pathway.
Gerondakis
S
S
Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Parkville, Victoria, Australia.
Morrice
N
N
Richardson
I B
IB
Wettenhall
R
R
Fecondo
J
J
Grumont
R J
RJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors; D015536:Down-Regulation / Q000235:genetics; D017930:Genes, Reporter; D005815:Genetic Code; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D010766:Phosphorylation; D011498:Protein Precursors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D051841:Transcription Factor RelB; D014157:Transcription Factors; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D011498:Protein Precursors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D051841:Transcription Factor RelB; D017868:Cyclic AMP-Dependent Protein Kinases