Chromatin loops are selectively anchored using scaffold/matrix-attachment regions.
The biological significance of nuclear scaffold/matrix-attachment regions (S/MARs) remains a topic of long-standing interest. The key to understanding S/MAR behavior relies on determining the physical attributes of in vivo S/MARs and whether they serve as rigid or flexible chromatin loop anchors. To analyze S/MAR behavior, single and multiple copies of the S/MAR-containing constructs were introduced into various host genomes of transgenic mice and transfected cell lines. These in vivo integration events provided a system to study the association and integration patterns of each introduced S/MAR. By utilizing FISH to visualize directly the localization of S/MARs on the nuclear matrix or chromatin loop, we were able to assign specific attributes to the S/MAR. Surprisingly, when multiple-copy S/MARs were introduced they were selected and used as nuclear matrix anchors in a discriminatory manner, even though they all contained identical primary sequences. This selection process was probably mediated by S/MAR availability including binding strength and copy number, as reflected by the expression profiles and association of multi-copy tandem inserted constructs. Whereas S/MARs functioned as the mediators of loop attachment, they were used in a selective and dynamic fashion. Consequently, S/MAR anchors were necessary but not sufficient for chromatin loops to form. These observations reconcile many seemingly contradictory attributes previously associated with S/MARs.
Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48202, USA. hheng@genetics.wayne.edu
Henry H Q
HH
Heng
Sandra
S
Goetze
Christine J
CJ
Ye
Guo
G
Liu
Joshua B
JB
Stevens
Steven W
SW
Bremer
Susan M
SM
Wykes
Juergen
J
Bode
Stephen A
SA
Krawetz
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002843:Chromatin / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D036961:Matrix Attachment Region Binding Proteins / Q000235:genetics / Q000378:metabolism; D045170:Matrix Attachment Regions / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D015530:Nuclear Matrix / Q000378:metabolism; D012313:RNA / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D002843:Chromatin; D036961:Matrix Attachment Region Binding Proteins; D011994:Recombinant Proteins; D012313:RNA