Western analysis of nuclear
extracts from COS-1 cells transfected with wild-type C/EBPβ expression vector (pCMV-C/EBPβ-wt); expression vectors with mutations
of the sORF-AUG and in which a 112-nt spacer was inserted between
the termination site of the sORF and AUG-2. (A)
Maps of the expression vectors used in these experiments. Vector
mtsORF has a mutation changing the sORF-AUG to -UUG, sORF(K2) has
a mutation changing the sORF to a perfect Kozak sequence, sORF(G8)
is altered to produce a sORF peptide of one methionine and eight
glycines rather than the normal MPPAAARRL, and spacer 112 has a
112-nt spacer inserted between the termination site of the sORF
and AUG-2. (B) Western blot analysis of proteins
from COS-1 cells: lane 1, proteins from non-transfected cells; lane
2, proteins from cells transfected with pMCV control vector; lanes
3–6, proteins from cells transfected with the expression
vector indicated. (C) Summary of protein pool levels
of C/EBPβ isoforms from several
independent experiments as shown in (B), mean ± SD.
The numbering of the grouped bars corresponds to the lanes in (B).
(D) Western blot analysis of proteins from COS-1
cells, lanes labeled as in (B). (E) Summary of
protein pool levels of C/EBPβ isoforms
from several independent experiments as shown in (D), mean ± SD.
The numbering of the grouped bars corresponds to the lanes in (D).