In the nucleus and cytoplasm of chicken erythroleukemic cells, prosomes containing the p23K subunit are found in centers of globin (pre-)mRNA processing and accumulation.
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.
Institut Jacques Monod, Université Paris 7, 2, Place Jussieu, Tour 43, Paris Cedex 05, 75251, France.
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De Conto
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Razin
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Geraud
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Arcangeletti
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Scherrer
D000818:Animals; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D002645:Chickens; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism*; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism*; D005914:Globins / Q000235:genetics*; D017403:In Situ Hybridization; D004915:Leukemia, Erythroblastic, Acute; D008856:Microscopy, Fluorescence; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000737:chemistry / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D014407:Tumor Cells, Cultured
D012322:RNA Precursors; D012333:RNA, Messenger; D005914:Globins; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease