Spatiotemporal Organization of AT and GC Rich DNA and Their Association With Transition Proteins TP1 and TP2 in Rat Condensing Spermatids

K.S. Ullas ¹, M.M. Pradeepa ¹, G. Nikhil ¹, N. Rammohan ¹ and M.R.S. Rao ^1*

¹ Department of Biochemistry, Indian Institute of Science, Bangalore, India (KSU,NR,MRSR), and Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, India (MMP,GN,MRSR)

^* To whom correspondence should be addressed. E-mail: mrsrao{at}jncasr.ac.in.

Submitted on December 30, 2008
Accepted on 27 May 2009

	Abstract

Transition proteins, TP1 and TP2, replace histones during mid-spermiogenesis (stages 12-15) and finally get replaced by protamines. TPs play a predominant role in DNA condensation and chromatin remodeling during mammalian spermiogenesis. TP2 is a zinc metalloprotein with two novel zinc finger modules, which condenses DNA in vitro in a GC preference manner. TP2 also localizes to nucleolus in transfected HeLa and Cos 7 cells suggesting a GC rich preference even in vivo. We have now studied the localization pattern of TP2 in the rat spermatid nucleus. Colocalization studies using GC selective DNA-binding dyes chromomycin A3 (CMA3) and 7-amino actinomycin D (AAD) and an AT-selective dye, 4’, 6-diamidino-2-phenylindole (DAPI), indicate that TP2 is preferentially localized to GC rich sequences. Interestingly, as spermatids mature TP2 and GC rich DNA moves towards nuclear periphery and in the late stages of spermatid maturation TP2 is predominantly localized at the nuclear periphery. Another interesting observation is the mutually exclusive localization of GC and AT rich DNA in the elongating and elongated spermatids. A combined immunofluorescence experiment with anti-TP2 and anti-TP1 antibodies revealed several foci of overlapping localization indicating that TP1 and TP2 may have concerted functional role during chromatin remodeling in mammalian spermiogenesis.

Key Words: spermiogenesis, DNA binding dyes, TP1, TP2, colocalization

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				M. M. Pradeepa, G. Nikhil, A. Hari Kishore, G. N. Bharath, T. K. Kundu, and M. R. S. Rao Acetylation of Transition Protein 2 (TP2) by KAT3B (p300) Alters Its DNA Condensation Property and Interaction with Putative Histone Chaperone NPM3 J. Biol. Chem., October 23, 2009; 284(43): 29956 - 29967. [Abstract] [Full Text] [PDF]

Guidelines | Subscriptions | About | exPRESS - Current - Archive | Business Information | Contact

The Journal of Histochemistry & Cytochemistry is owned, published, and licensed by The Histochemical Society © 2009