TATA-Dependent andTATA-Independent Function oftheBasaland HeatShockElements ofa Humanhsp7OPromoter

Wehavecharacterized theinteractions between theTATAelement andother sequenceelements ofahuman heatshockprotein 70(hsp7O) promoterbya mutational approach. Expression ofa distal element ofthis promoter requires an intact TATAelement inhumancelllines. Thehsp7OTATAelement can befunctionally replaced forthis interaction byTATAelements fromthesimian virus 40early andadenovirus EIlapromoters. TheTATA element inthis promotertherefore bothdetermines theappropriate startsite anddetermines strength byallowing function ofthedistal element. Incontrast, three proximal upstreamelements necessary forbasal andheat-regulated transcription haveno requirement either fora TATA element orforany other proximal element. Thebehavior ofpromoters multiply mutantinthese proximal elements implies thatthese elements function independently. We examined theinteraction between theheatshockelement (HSE)andthe TATAelement asthedistance between thetwofactor-binding sites was increased. Itwas necessarytocreate amutantHSEwith anextended consensussequenceinorder fortheHSEtofunction atadistance. Movingthis extended HSE500bases upstream didnotincrease itsdependence on theTATAelement, suggesting thatthe TATA independence ofthis element isintrinsic toitsfunction andisnotdetermined bydistance fromthe promoter. Mammalian promoters transcribed byRNA polymerase II contain multiple sequence elements, eachofwhichiscapableofbinding specific protein factors (forreviews, see references 8and16). Theseelements canbespread outover several hundred toseveral thousand basepairs. Whereas in vivomutational analysis hasshownthatmultiple elements cancontribute totheexpression ofagene,little isknown abouthowtherespective factors interact toregulate transcription. Biochemical andgenetic evidence suggests that upstream