HCaRG, a novel calcium-regulated gene coding for a nuclear protein, is potentially involved in the regulation of cell proliferation.
Since a negative calcium balance is present in spontaneously hypertensive rats, we searched for the gene(s) involved in this dysregulation. A cDNA library was constructed from the spontaneously hypertensive rat parathyroid gland, which is a key regulator of serum-ionized calcium. From seven overlapping DNA fragments, a 1100-base pair novel cDNA containing an open reading frame of 224 codons was reconstituted. This novel gene, named HCaRG (hypertension-related, calcium-regulated gene), was negatively regulated by extracellular calcium concentration, and its basal mRNA levels were higher in hypertensive animals. The deduced protein showed no transmembrane domain, 67% alpha-helix content, a mutated calcium-binding site (EF-hand motif), four putative "leucine zipper" motifs, and a nuclear receptor-binding domain. At the subcellular level, HCaRG had a nuclear localization. We cloned the human homolog of this gene. Sequence comparison revealed 80% homology between rats and humans at the nucleotide and amino acid sequences. Tissue distribution showed a preponderance in the heart, stomach, jejunum, kidney (tubular fraction), liver, and adrenal gland (mainly in the medulla). HCaRG mRNA was significantly more expressed in adult than in fetal organs, and its levels were decreased in tumors and cancerous cell lines. We observed that after 60-min ischemia followed by reperfusion, HCaRG mRNA declined rapidly in contrast with an increase in c-myc mRNA. Its levels then rose steadily to exceed base line at 48 h of reperfusion. HEK293 cells stably transfected with HCaRG exhibited much lower proliferation, as shown by cell count and [(3)H]thymidine incorporation. Taken together, our results suggest that HCaRG is a nuclear protein potentially involved in the control of cell proliferation.
Centre de recherche, Centre hospitalier de l'Université de Montréal, Montréal, Québec H2W 1T8, Canada.
N
N
Solban
H P
HP
Jia
S
S
Richard
S
S
Tremblay
A M
AM
Devlin
J
J
Peng
F
F
Gossard
D F
DF
Guo
G
G
Morel
P
P
Hamet
R
R
Lewanczuk
J
J
Tremblay
D048868:Adaptor Proteins, Signal Transducing; D000311:Adrenal Glands / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000494:pharmacology*; D018797:Cell Cycle Proteins; D002455:Cell Division; D002460:Cell Line; D003001:Cloning, Molecular; D020832:EF Hand Motifs; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D006973:Hypertension / Q000378:metabolism; D017403:In Situ Hybridization; D007668:Kidney / Q000378:metabolism; D016350:Leucine Zippers; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010280:Parathyroid Glands / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D015427:Reperfusion Injury; D017386:Sequence Homology, Amino Acid
D048868:Adaptor Proteins, Signal Transducing; C485926:COMMD5 protein, human; D018797:Cell Cycle Proteins; C415469:Commd5 protein, rat; D009687:Nuclear Proteins; D012333:RNA, Messenger; D002118:Calcium