sentence: The results indicate that the nucleoplasmic and cytoplasmic preribosomes are released at the SN1 step , the intermediate preribosomes present in more soluble or more accessible nucleolar regions are extracted in the SN2 ( note that RRP12 is >80 % nucleolar and is mostly concentrated in the SN2 ) , and the early preribosomal complexes formed in inner nucleolar regions are solubilized in the SN3.To further test the performance of the PSE method , we carried out extractions in cells that exhibit aberrant localization of preribosomal components due to either a block in pre-rRNA transcription ( caused by treatment with actinomycin D ( ActD ) ) or in nuclear export ( caused by the leptomycin B ( LMB ) - mediated inhibition of CRM1 ) .