Nucleolar organizer

Aziz, J.B., N.M. Akrawi, and G.A. Nassori. 1991. The effect of chronic toxicity of copper on the activity of Balbiani rings and nucleolar organizing region in the salivary gland chromosomes of Chironomus ninevah larvae. Environ. Pollut. 69 125-130. 

Figure 26-15 (A) Numbering and staining patterns (G-banding) of human chromosomes. The horizontal line marks the centromeres. Chromosomes 13,14,15, 21, and 22 have nucleolar organizers located at the constrictions in their short arms. From Alberts et al.297 Adapted from U. Franke.298 (B) Map of genetic defects identified in X chromosomes by 1995. From McKusick and Amberger.294...

Figure 28-15 Steps in ribosome formation in the nucleolus. From Sommerville.524 Abbreviations are NOR, nucleolar organizing regions RNP, ribonucleoproteins.

As is indicated in Fig. 28-15, transcription is thought to occur from the loops of DNA that form the nucleolar organizing region. The 100-kDa nucleolin, the major protein of the nucleolus, binds to the non-transcribed spacer sequences in the DNA.529-530 It also binds to the newly formed transcripts, as do various proteins that enter the nucleus from the cytoplasm.524531 More than 270 proteins, many of which participate in synthesis of ribosomes, have been detected in the nucleolus.5313 Some of these proteins, acting together with the snoRNAs discussed in the next section, catalyze hydrolytic cleavage of the pre-rRNA molecules. For completion of pre-ribosomal particles additional protein molecules enter the nucleolus and associate with the pre-rRNA particles, then diffuse out of the nucleus. 

Hirai, H. (1988) Paragonimus ohirai identification of nucleolar organizer regions (NORs) and silver nitrate staining pattern in spermatogenesis. Experimental Parasitology 67, 281-286. 

Kale, A., Soylemez, F., and Ensari, A. 2001. Expressions of proliferation markers (Ki-67, proliferating cell nuclear antigen, and silver-staining nucleolar organizer regions) and of p53 tumor protein in gestational trophoblastic disease. Am. J. Obstet. Gynecol. 184 561—514. 

Ofner, D., Bankfalvi, A., Riechemann, K., Bier, B., Bocker, W., and Schmid, K. W. 1994. Wet autoclave pretreatment improves the visualization of silver stained nucleolar organizer region associated proteins (AgNORs) in routinely formalin-fixed and paraffin-embedded tissues. Mod. Pathol. 2 946-950. 

Ofner, D., Bier, B., Heinrichs, S., Berghom, M., Dtinser, M., and Hagemann, H. E. 1996. Demonstration of silver-stained nucleolar organizer regions associated proteins (AgNORs) after wet autoclave pretreatment in breast carcinoma. Breast Cancer Res. Treat. 59 165-167. 

Nucleolar organizing region (NOR) Area of the nucleolus where a great deal of rRNA transcription and synthesis occurs. 

Mena H, Rushing EJ, Ribas JL, et al. Tumors of pineal parenchymal cells A correlation of histological features, including nucleolar organizer regions, with survival in 35 cases. Hum Pathol. 1995 26 20-30. 

Mitsui H (1992) [AgNORs (Ag nucleolar organizer regions)]. NipponRinsho 50 2349-2354 Review Article 18 Refs... 

Pre-rRNA Genes Are Similar in All Eukaryotes and Function as Nucleolar Organizers... 

Bloom, S. E., and Goodpasture, C. (1976). An improved technique for selective silver staining of nucleolar organizer regions in human chromosomes. Hum. Genet. 34,199-206. 

Crocker, J. (1990). Nucleolar organizer regions. Curr. Top. Pathol. 82, 91-149. 

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