sentence: Collectively , our data reveal that there are two distinctive and biochemically separable pools of ~ 40S precursors : ( i ) An earlier set of intermediates ( referred to hereafter as pre40S-No1 ) , which includes the initial complexes formed upon generation of the 18S-E pre-rRNA , contains ENP1 , HEATR1 , RRP12 , NOP14 , NOC4L , and intact 18S-E pre-rRNA species .