Page 1 \ ?^p 6r.1 CELL CYCLE CONTROL OF HUMAN H4 ...

azh F: cer cyde c@trot ol H4 G@e tuantdtotbn
ed FAM'15/CAT, but in the abs€nca of lhe potenlially conlounding
parameler of binding site spacing, unequivocally establishes rhat the HiNF.
M/|FF-2 recoqnition elemenl is ossernialior high level H4 transcriplion.
Muranr [lPM-17 €ipressos th6 CAT r6porter gene ai a morc redlced
levelthan MSP-16 (6 to s lold reduction) (F g. 30), simlar to mlrant i,IC-7 (s€o
Fig.28). Thus, while mutalions in the H|NF-P/H4TF-2 and H|NF-D binding
siles each by itsell do not alf€cr tl4 promoter ac vity (murants GT 9 and SUB-
1 1 ; see Fig. 28), it appea.s t'at thes€ factors play important auxiliary roles in
derermining H4 gene rransciplion.
Mutations in the IGM-18/CAT clnsruct dedeGe reporter gens
expression approximalely 3 lold relativo to rhe wildrype H4 promoter, but
expression with IGM-18/CAT r€mains signilic€ntly hgher than that observed
lor l',4PM.17lCAl As bolh oi thos€ consrrucrs do not bind HNF-P/H4TF,2
and havc similar redlced afiinity lof HNF-D (Fig. 30), th€se mulants dttief
only in lhe relarive srrenqth ot t-UNF-lV/tRF-2 binding to Site tt. Th!s,
quaniitative ditferences n occupancy ol Sit€ ll by HiNF-M/lRF-2 in vitrc appaal
to resull in conespondlng quantitative difierencas in H4 promots ac-liviry /h
conlributions ol the H4,slte ll blndlng proiehs ro human
hislons H4 genelranscripiion dudng the cellcycte
Studies desc.ibed in pfevlous section indlcate hal marimal
transcriplion oI celcyce controled histone H4 genes requnes lhe iniegrated
activities oi at least three dislnct lransdpron taclors, HiNF-1V/tnF,2, HiNF,
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