By Eva Kuehnen
FRANKFURT, May 27 (Reuters) - European shares gave up early gains and fell to a four-week low on Tuesday as losses in banks and GlaxoSmithKline <GSK.L> offset gains in Vodafone <VOD.L> and the impact of acquisition talk in the brewing sector.
By 0921 GMT, the pan-European FTSEurofirst 300 index <
> was down 0.44 percent at 1,313.73 points, its lowest level since late April, after rising to an intraday high at 1,326.60.The index fell more than 3 percent last week, and dipped 0.2 percent on Monday when financial markets in the United States and the UK were closed for public holidays.
Over the past six months, banks have taken large writedowns as a result of the credit market crisis sparked by a collapse in the market for U.S. mortgages, and traders said markets were still edgy.
The DJ Stoxx 600's bank index <.SX7P> was down 0.6 percent.
"There is the rumour of further writedowns in the banking sector. We don't know anything specific, but the market is reacting very nervously," a trader said.
Other traders said that there was talk of banks having funding problems, but did not mention any names.
The latest ECB figures showed that a bank or banks borrowed 538 million euros from the central bank on Monday, which rekindled fears about the health of the financial system.
Swiss bank UBS <UBSN.VX> was down 1.9 percent after trading ex-rights and Royal Bank of Scotland <RBS.L> dropped 1.6 percent, ING <ING.AS> fell 1.5 percent and BNP Paribas <BNPP.PA> dropped 1.4 percent.
GlaxoSmithKline <GSK.L> fell 1 percent after Morgan Stanley downgraded Europe's biggest drugmaker to "underweight" from "equal-weight".
A Lehman downgrade weighed on Norwegian fertiliser group Yara <YAR.OL>, which fell 4.5 percent.
Around Europe, Germany's DAX index <
> fell 0.6 percent percent and France's CAC 40 < > dropped 0.8 percent. Only the UK's FTSE 100 index < > managed to hold on to earlier gains and was up 0.1 percent, mainly thanks to gains in Vodafone.RIGHT TIMING
Vodafone shares rose 1.2 percent after the world's largest mobile phone company by revenue said it met full-year forecasts and announced the exit of Chief Executive Arun Sarin, who will be replaced by his deputy chief executive and head of the European business, Vittorio Colao.
"Vittorio Colao has been groomed for this job and the timing is right to replace Arun Sarin," said David Buik in a note.
On the merger and acquisition front, SABMiller <SAB.L> soared 6.5 percent following a report in the Financial Times over the weekend that Belgian brewer InBev <INTB.BR> was not only working on a $46 billion takeover bid for Anheuser-Busch <BUD.N> but was also casting an acquisitive eye over SABMiller should a bid for Anheuser fail.
InBev shares dropped 1.9 percent.
Investors awaited reports on the U.S. housing sector and the Conference Board's index of consumer sentiment, both due at 1400 GMT, for clues about the health of the world's biggest economy.
(Reporting by Eva Kuehnen; editing by Rory Channing)