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Nuclear Localization of the Saccharomyces cerevisiae HMG Protein NHP6A Occurs by a Ran‐Independent Nonclassical Pathway
Author(s) -
Yen YiMeng,
Roberts Paul M.,
Johnson Reid C.
Publication year - 2001
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1034/j.1600-0854.2001.20703.x
Subject(s) - importin , ran , biology , nuclear transport , nuclear localization sequence , nuclear protein , saccharomyces cerevisiae , high mobility group , microbiology and biotechnology , cell nucleus , binding domain , nls , dna binding domain , nuclear export signal , biochemistry , binding site , nucleus , yeast , gene , transcription factor
The Saccharomyces cerevisiae non‐histone protein 6‐A (NHP6A) is a member of the high‐mobility group 1/2 protein family that bind and bend DNA of mixed sequence. NHP6A has only one high‐mobility group 1/2 DNA binding domain and also requires a 16‐amino‐acid basic tail at its N‐terminus for DNA binding. We show in this report that nuclear accumulation of NHP6A is strictly correlated with its DNA binding properties since only nonhistone protein 6 A–green fluorescent protein chimeras that were competent for DNA binding were localized to the nucleus. Despite the requirement for basic residues within the N‐terminal segment for DNA binding and nuclear accumulation, this region does not appear to contain a nuclear localization signal. Moreover, NHP6A does not bind to the yeast nuclear localization signal receptor SRP1 and nuclear targeting of NHP6A does not require the function of the 14 different importins. Unlike histone H2B1 which contains a classical nuclear localization signal, entry of NHP6A into the nucleus was found to be independent of Ran as judged by coexpression of Ran GTPase mutants and was shown to occur at 0 °C after a 15‐min induction. These unusual properties lead us to suggest that NHP6A entry into the nucleus proceeds by a nonclassical Ran‐independent pathway.