Changes in replication, nuclear location, and expression of the Igh locus after fusion of a pre-B cell line with a T cell line.
We have previously observed that replication and nuclear location of the murine Igh locus are developmentally regulated during B cell differentiation. In non-B, B, and plasma cells, sequences near the 3' end of the Igh locus replicate early in S while upstream Vh sequences replicate late in S, and the Igh locus is located near the nuclear periphery. In fact, in MEL non-B cells, replication of a 500-kb segment containing Igh-C and flanking sequences occurs progressively later throughout S by 3' to 5' unidirectional fork movement. In contrast, in pro- and pre-B cells, the entire 3-Mb Igh locus is located away from the nuclear periphery and replicates early in S by forks progressing in both directions. In this study, using an 18-81 (pre-B) x BW5147 (T) cell fusion system in which Igh expression is extinguished, we found that in all Igh alleles, Vh sequences replicated later in S than 3' Igh sequences (similar to that detected in BW5147), but the Igh locus was situated away from the nuclear periphery (similar to that observed in 18-81). Thus, pre-B cell-derived Igh genes had changes in replication timing, but not in nuclear location, whereas T cell-derived Igh genes changed their nuclear location but not their replication timing. These data are consistent with the silencing of a pre-B cell-specific replication program in the fusion hybrid cells and independent regulation of the nuclear location of Igh loci.
Zhou
Jie
J
Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Saleque
Shireen
S
Ermakova
Olga
O
Sepulveda
Manuel A
MA
Yang
Qiaoxin
Q
Eckhardt
Laurel A
LA
Schildkraut
Carl L
CL
Birshtein
Barbara K
BK
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D001483:Base Sequence; D002459:Cell Fusion; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000235:genetics*; D004261:DNA Replication; D005819:Genetic Markers; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D006822:Hybrid Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D007143:Immunoglobulin Heavy Chains / Q000096:biosynthesis* / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D013601:T-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism
D005819:Genetic Markers; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region