De Conto F, Razin S V, Geraud G, Arcangeletti C, Scherrer K
Institut Jacques Monod, Université Paris 7, 2, Place Jussieu, Tour 43, Paris Cedex 05, 75251, France.
Exp Cell Res. 1999 Aug 1;250(2):569-75. doi: 10.1006/excr.1999.4556.
Prosomes were originally identified as 20S particles associated with untranslated mRNA; they also constitute the core of the 26S proteasomes. The cellular distribution of three types of prosomes characterized by the presence of subunits with molecular masses of 23, 27, and 30 kDa was analyzed using an immunocytochemical approach on cultured chicken erythroblasts. The prosomes containing the p27K and p30K subunits were found in diffuse distribution in both nuclei and cytoplasm. In contrast, the prosomes containing the p23K subunit, although relatively rare in the nuclear space, were found concentrated in one or two large spots. Using in situ hybridization with an alpha(A)-globin gene-specific riboprobe we found that the p23K-type prosomes colocalize in the nucleus with centers of globin (pre-)mRNA processing, and of mRNA accumulation in the cytoplasm. This result suggests there is local coincidence of specific-type prosome function with processing and, possibly, transport of a particular kind of (pre-)mRNA.
原核小体最初被鉴定为与未翻译的mRNA相关的20S颗粒；它们也是26S蛋白酶体的核心。使用免疫细胞化学方法，对培养的鸡红细胞进行分析，以研究三种类型的原核小体（其特征是存在分子量为23、27和30 kDa的亚基）的细胞分布。含有p27K和p30K亚基的原核小体在细胞核和细胞质中呈弥散分布。相比之下，含有p23K亚基的原核小体虽然在核空间中相对较少，但集中在一两个大的斑点中。使用α(A)-珠蛋白基因特异性核糖探针进行原位杂交，我们发现p23K型原核小体在细胞核中与珠蛋白（前体）mRNA加工中心以及细胞质中mRNA积累中心共定位。这一结果表明，特定类型的原核小体功能与特定种类的（前体）mRNA的加工以及可能的转运在局部存在一致性。
