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

,r1z F Cett cy.te connot ol H4 Gene ftansc.ipt.n
For example, oliat€s and lunqi do not show rhe post'transcriplional Pathway
which regulares lhs processing ot pr€ mRNAI bul lho olhel rwo pathways are
operaiv6 and all €ut6rycli€9 ll is known lhai lhe
hanscriptional rBgulalion is mo.e Prominenl lhsn the Posi_lransfiiptional
regulalion ol rho level ol hlstong mFNAs ln som€ lowsr eukaryol€s The posl
rranscrip onal coolrol of hislon€ mFNA sccl,mulalion in the cetl cycle ot lowe.
eukaryotes has been syslematically studlad only in budding yeast For
example, ifl yeast th6 hislone gene fianscn ion is hardly se€n in ihe eany G1
Phase, blt tacl ilaled 10 . 20 lold in lal6 Gl Phase (Hsrcford d ar , 1982) This
me4s hal lhis incre6e i. vansc ption is the sam€ as
accumllationol mFNAduring lh€ S'Phds6. (Hareford €l a/., l9SliHeretordel
3/., 1982) s.d,u her wien yeast colls 6ro block€d during s'phase ihe major
effect ls to tum ofl lhe transfiiprion machin€ry ol hisbn€ genes ralher rhan to
deslabii2e th6 hislon€ mANAs (Lycan €l 3/., 1987) lt is shown thal wh€n
some oher yeasl hisloDe geaes were axprcssod conslilutivaly signilicanl
fuctuations we.e obs€rved in the lev6l ol hisionB mFNA du ng lhs cell cycle
so rhat these mANAs clnunuously accumulaled in s-Phase (Lvcan er a/. 1987;
Biorogical and blochemicat Paramel6.s ihat regulal€the hrstone 9en€
The several reouialory mschanisms conirolth€ timing and coordrnalion
ol hinone gene expression. For examPle O non'cen cycle .eguhed histone
gene expression can occur during allstag€sol d€vsloPm6nlln manv dllferent
lisslest (ii) Hi$one gene expression can be resPonsive to c6ll signallng