THE HALF-LIFE OF C-MYC MESSENGER-RNA IN GROWING AND SERUM-STIMULATED CELLS - INFLUENCE OF THE CODING AND 3' UNTRANSLATED REGIONS AND ROLE OF RIBOSOME TRANSLOCATION
Dj. Herrick et J. Ross, THE HALF-LIFE OF C-MYC MESSENGER-RNA IN GROWING AND SERUM-STIMULATED CELLS - INFLUENCE OF THE CODING AND 3' UNTRANSLATED REGIONS AND ROLE OF RIBOSOME TRANSLOCATION, Molecular and cellular biology, 14(3), 1994, pp. 2119-2128
c-myc mRNA contains at least two discrete sequence elements that accou
nt for its short half-life, one in the 3' untranslated region and the
other in the carboxy-terminal coding region (coding-region determinant
). To investigate the function of each determinant, one or both were f
used in frame to portions of a gene encoding long-lived beta-globin mR
NA. Each chimeric gene was stably transfected into HeLa and NIH 3T3 ce
lls and was transcribed from a constitutive cytomegalovirus promoter o
r from a serum-regulated c-fos promoter, respectively. The steady-stat
e levels of the chimeric mRNAs in exponentially growing HeLa cells wer
e compared, and their half-lives were measured by two independent meth
ods: (i) in actinomycin D-treated HeLa cells and (ii) after serum addi
tion to starved 3T3 cells. By each method, mRNAs containing either ins
tability determinant were less stable than beta-globin mRNA. mRNA cont
aining only the c-myc 3' untranslated region was not significantly mor
e stable than mRNA with both determinants. In a cell-free mRNA decay s
ystem containing polysomes from transfected HeLa cells, mRNA containin
g the coding-region determinant was destabilized by addition of a spec
ific RNA competitor, whereas mRNA containing only the 3' untranslated
region was unaffected. When a stop codon was inserted upstream of the
coding-region determinant, the chimeric mRNA was stabilized approximat
ely twofold. These and other data suggest that degradation involving t
he coding-region determinant occurs most efficiently when ribosomes ar
e translating the determinant.